H.1 Reference Design and Safety Guidelines for the Plumbing Designer
H.2 Building Design Considerations
H.3 Plumbing Systems
H.4 Sanitary and Waste System
H.5 Storm Drainage Systems
H.6 Laboratory Safety Equipment
H.7 Compressed-Gas Systems
H.8 Vacuum Systems
H.9 Natural Gas/Fuel Systems
H.10 Backflow Prevention (BFP)
H.11 Pure Water Systems
H.12 Process Water Systems

H.1 Reference Design and Safety Guidelines for the Plumbing Designer

The NIH is a progressive and dynamic biomedical research institution where state-of-the-art medicine is the standard practice. To support state-of-the-art research and medical care, the facilities must also be state of the art. It is the NIH’s intent to build and maintain the physical plant and facilities in accordance with the latest standards.

It has been the NIH experience that renovation/rehabilitation of existing facilities do not lend themselves to incorporating the “latest” standards of the industry, primarily because of outdated and inadequate plumbing systems.

The architect/engineer (A/E) should be alerted to this situation and make an evaluation early in the design stage to determine the feasibility of implementing the latest standard. The A/E should document such findings, provide recommendations, and report them to the Project Officer for a decision on how to proceed and to request a variation from the existing Design Guidelines if necessary.

The A/E design firm should use and comply with, as a minimum, the latest issue of the following design and safety guidelines. In addition, the A/E shall use other safety guidelines received from the NIH Project Officer or as required by program. The A/E should utilize the latest versions of guidelines available at the time the project proceeds with schematic design.

The criteria include, but are not limited to, the following:

• The International Building Code and the International Plumbing Code: International Code Council, Inc., and Building Officials and Code Administrators (BOCA) International, Inc.: 4051 West Flossmoor Road, Country Club Hills, IL 60477-5795.
• American National Standard for Emergency Eyewash and Shower Equipment (ANSI Standards Z358.1): Industrial Safety Equipment Association, New York, American National Standards Institute (ANSI).
• Planning and Design of Laboratory Facilities: Baker, J.H., Houang, L. (1983) the World Health Organization (WHO), Offset Publications, 72:45-71.6.
• Occupational Safety and Health Standards, CFR 29, Part 1910: U.S. Department of Labor, Occupational Safety and Health Administration (OSHA).
• Guidelines for Research Involving Recombinant DNA Molecules: U.S. Department of Health and Human Services, U.S. Public Health Service, National Institutes of Health, Federal Register, Vol. 51, No. 88: 16957-16985, Bethesda, MD: National Institutes of Health.
• Laboratory Safety Monograph: A Supplement to the NIH Guidelines for Recombinant DNA Research, U.S. Department of Health and Human Services, U.S. Public Health Service, National Institutes of Health, Bethesda, MD: National Institutes of Health.
• Guidelines for Laboratory Design: Health and Safety Considerations: DiBernardinis, L., and J.S. Baum, M.W. First, H.T. Gatewood, E.F. Gordon, and A.K. Seth. 1987. New York: John Wiley and Sons.
• Biosafety in Microbiological and Biomedical Laboratories: U.S. Department of Health and Human Services. Washington, DC: Public Health Service, Centers for Disease Control and Prevention, and National Institutes of Health, HHS Pub. No. (NIH)88-8395.
• NIH Guidelines for the Laboratory Use of Chemical Carcinogens: U.S. Department of Health and Human Services, Bethesda, MD: National Institutes of Health, NIH Pub. No. 81-2385.
• National Fire Codes, all volumes: National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02269-9101.
• Guide for the Care and Use of Laboratory Animals: U.S. Department of Health and Human Services, Bethesda, MD: National Institutes of Health, Pub. No. 86-23.
• Guidelines for Design and Construction of Hospital and Health Care Facilities: The American Institute of Architects Committee on Architecture for Health with assistance from the U.S. Department of Health and Human Services. American Institute of Architects Press, 1735 New York Avenue, NW, Washington, DC 20006.
• Medical Laboratory Planning and Design: College of American Pathologists, Skokie, IL.
• American Society of Hospital Engineering, all volumes: American Hospital Association, 840 North Lake Shore Drive, Chicago, IL 60611.
• Regulations Governing the Installation of Plumbing, Gas Fitting and Sewer Cleaning in the Washington Suburban Sanitary District: Washington Suburban Sanitary Commission (WSSC), 4017 Hamilton Street, Hyattsville, MD 20781.
• Standards for Medical-Surgical Vacuum Systems in Hospitals, PAMPHLET, p. 21, Compressed Gas Association (CGA).
• Uniform Federal Accessibility Standards, FED STD 795.
• The Americans with Disabilities Act Accessibility Guidelines.
• ANSI Standard Z 358.1: American National Standards Institute, Inc., 1430 Broadway, New York, NY 10018.
• ASPE Data Books, all volumes and supplements: American Society of Plumbing Engineers (ASPE), 3617 Thousand Oaks Boulevard, Suite 210, Westlake, CA 91362.
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H.2 Building Design Considerations

The A/E should include at the completion of the schematic design a report on proposed plumbing systems in the Basis of Design. The report should justify the complete design concept of the A/E. Detailed plumbing design criteria, computations, schematic system diagrams, commissioning plan criteria, economic analysis, and life-cycle costing comparisons shall be included as a part of the Basis of Design report.

Operational and repair manuals for all plumbing supplied equipment on the project are required and should be called for in the specifications. A meeting shall be specified to turn over the equipment inventory and manuals to the Office of Research Facilities.

The A/E should include, as a minimum, evaluation of the following topics prior to completion of the schematic design phase. Results of the evaluation should be defined in the Basis of Design report.

General Plumbing:

• Project utilities and capacities
• Descriptions of various services
• Proposed piping system, its components and materials
• Storm water management plan for the building
• Plumbing equipment locations and access
• Applicable codes, guidelines, and standards
• Basic design criteria of systems (sizing, pressures, zoning, temperature, etc.)

Fixtures and Trim:

• Distribution of plumbing services
• Zoning, modularity, and flexibility
• Water conservation plan and opportunities
• Control methodology
• Redundancy and reliability

Commissioning Plan Criteria:

• Space required for storage/spare parts/maintenance administration
• Laboratory safety equipment
• Compressed gas and air systems
• Vacuum systems
• Natural gas/fuel systems
• Pure water systems
• Process/animal water systems
• Filtration requirements
• Measuring and monitoring methodology

H.2.1 Plumbing Systems Inspections: The installation of plumbing systems at the NIH is generally not inspected by municipal plumbing inspectors, as would be required and typical of installations off campus. As such, it is critical that the design engineer work with the NIH to ensure plumbing installations are code compliant and meet the intent of the design documents and NIH Guidelines. In some cases, the A/E may be requested to provide inspection services, and this should be considered during the contract negotiations. In any case, the A/E must not only perform field reports with the intent of observing general compliance with design documents, but also should assist the NIH in recognizing non-codecompliant workmanship. It is the intent of the NIH that each system installation meet or exceed applicable codes, inspection, and testing requirements as well as requirements of the NIH Design Policy and Guidelines.

In general, each plumbing installation should be inspected and thoroughly tested prior to concealment. Plumbing work should be reviewed for proper slope, joints, layout, materials, and installation. Testing should be provided and witnessed prior to backfill, concealment in walls, and again at final completion. All installations shall be tested and inspected to at least the same degree as would be required for installations off campus. Final system tests should consider proper installation and adjustment, code compliance, completeness, and leakage. The engineer should include in specifications that systems must be tested and inspected, and that qualified licensed personnel in accordance with WSSC requirements shall perform work.

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H.3 Plumbing Systems

H.3.1 Types of Systems: The plumbing systems at the NIH are categorized as domestic potable water plumbing systems and industrial nonpotable water plumbing systems. In addition, there are medical/laboratory gas and vacuum systems, fuel systems, various types of pure water systems, and process water systems. All plumbing systems installed in NIH buildings shall meet the requirements of the WSSC governing the installation of plumbing and gas fitting regulations unless otherwise stated by these guidelines.

Domestic plumbing systems should consist of potable hot and cold water piping, domestic water heaters, waste and vent piping, stormwater, and other common general use systems. These systems typically serve areas such as toilets, locker rooms, kitchens, laundries, patient rooms, and so on, which may be common to all building types.

Industrial plumbing systems should consist of, but not be limited to, nonpotable hot and cold water piping, water heaters, acid waste and vent, conditioned water systems, medical/laboratory gas and vacuum systems, rackwashing and cagewashing equipment, glassware-washing equipment, safety equipment, and process water systems. Plumbing requirements are often dictated by end users during the design phase and are subject to change because of improving equipment technology and the need to remain state of the art when the construction process is completed. The design engineer must clearly understand the wide range of utility requirements and design the distribution systems to be flexible and support future connections.

Plumbing systems should support the needs of the building occupants, be easily maintained and operated, have reliable and redundant components, and be efficient to operate. These systems should not impose harm on user equipment because of excessive pressures, improper water temperature, or inadequate drainage facilities. Contained pieces of equipment have numerous piping connections, which must be concisely detailed and engineered in the contract documents.

H.3.1.1 Functional Design Considerations: Special consideration should be given to the design concepts discussed below in order to provide long-term capability, flexibility, and maintainability.

• Overall, the design of the piping distribution should be based on a modular layout, even though this arrangement sometimes limits the configuration and locating of individual spaces.
• Piping distribution systems should consist of vertical risers located in chases, horizontal mains, and individual room runouts to accommodate the architectural layout of the building. In general, the NIH uses a utility corridor concept, or interstitial space concept, in the case of a corridor utility shaft concept, or an external utility shaft concept. The design approach should result in a repetitive and standardized grid arrangement of the risers, mains, branches, and runouts. Piping and valving arrangements shall allow for easy shutdown of individual laboratories, floors, and zones of the system without affecting adjacent areas for modifications and maintenance to the systems. The primary goal for vertical distribution systems is to minimize floor penetrations in laboratory areas.
• Ideally, piped services, except waste and vent systems, should be distributed in a double-ended horizontal loop that may be sectionalized for alterations and repair. A utility corridor concept, either interior or exterior, should be utilized with vertical risers feeding horizontal loops.
• Isolation valves should be provided to accommodate easy maintenance at each module, group of toilet rooms, program suite, or other branches where routine service will be required. All isolation valves should be accessible and located on the floor being served or in the interstitial space serving the respective program area.
• Horizontal distribution mains should be located on the floor of the equipment or fixtures to be served. It is not desirable to upfeed through a floor slab to fixtures above unless absolutely required by rough-in location.
• Adequate space should be provided for accessibility to permit modifications and maintenance to the system. Service pipe runouts placed at regular intervals in service shafts or utility corridors will ensure maximum accessibility for future connections with a minimum of disruption to research programs in adjacent spaces. Runouts shall be valved and capped.
• All equipment that must be serviced, operated, or maintained should be located in fully accessible positions. Equipment should include, but not be limited to, valves, cleanouts, motors, controllers, dampers and drain points, etc. Where required, 1.9 mm steel access panels shall be provided. Doors installed in fire-rated walls or shafts shall be labeled and shall match the rating of the construction. Doors shall be of sufficient size to allow access to all components; minimum size shall be 300 by 400 mm. Doors in toilet rooms shall be Type 304 stainless steel or have a chrome-plated finish.
• Pipe sizing should be designed on calculated flow rates, acceptable diversity factors, minimum and maximum velocity limitations, and reasonable allowable pressure drops for the various types of systems. Where there are architectural and structural allowances for building additions, pipe sizes shall be increased to allow for building expansion.
• Piping material should be selected on the basis of system pressures, temperatures, and the type of medium flowing to withstand corrosion and erosion. Piping and fittings in all NIH buildings shall be specified in accordance with Table F.6 in General Design Guidelines, Section: Mechanical, Piping Systems.
• All plumbing piping systems must be identified using pipe labels as required by General Design Guidelines, Section: Mechanical, Systems Identification. Difficulty in identifying individual pipelines creates serious potential for cross-contamination.
• Proper assessment of required water resources and quality is essential for NIH buildings. The quality of water required (distilled, deionized, or treated by reverse osmosis with deionizers) needs to be determined so that the proper selection of water treatment equipment can be made.
• Proper backflow protection should be provided to protect domestic potable water systems from industrial nonpotable systems and miscellaneous equipment.
• Provision of proper pipe sleeving at penetrations through floors is especially important. Many functions have been disrupted or damaged because of leakage on floors above passing through pipe penetrations. Pipe sleeves should extend at least 50 mm above the floor and 25 mm below the floor and should include a built-in water stop and appropriate seal. All penetrations through rated structure shall be properly fire/smoke stopped.
• Plumbing fixtures and trim should be carefully selected to meet the requirements of building users. Fixtures should be of the low-consumption type as defined by WSSC and have flow restrictors as required. Elbow, knee, foot, and automatically activated faucets shall be provided as dictated by program requirements.
• Submicron HEPA filters between vacuum traps and fixture valves should be provided to eliminate microorganisms in hazardous areas such as BSL-3 or BSL-4 labs.
• Electric water coolers should be specified to use chlorofluorocarbon (CFC or HCFC)-free refrigerants and be completely assembled without the use of lead solder.
• All piping systems designed for NIH buildings should be specified with a joint method prohibiting the use of lead solder.
• Building-wide water softeners and treatment equipment are generally not required for
  NIH buildings because of the good quality of water from WSSC’s distribution network. Program requirements suggesting the use of such equipment shall be seriously challenged by the A/E and justified in the early design stages.

H.3.1.2 Fixtures and Trim: Those items should be selected which aid in maintenance of the aseptic environment. Plumbing fixtures should be selected in accordance with applicable national standards to provide appropriate function, durability, quality, and ease of maintenance. The A/E should consider sanitation, durability, and potential for cross-infection in selection of plumbing fixtures, which should be made of nonabsorptive, acid-resistant materials. Lavatory centersets, except in general public areas, nurseries, and scrub areas, should be fitted with wrist blade handles or hard wired and on emergency power sensor-operated fixtures. Sinks in nurseries should have retractable, foot-operated valves while those in scrub areas will have either foot-operated valves that pivot upward for cleaning or knee-operated valves. Clinical sinks will have an integral trap in which the upper portion of the water surface provides a visible trap seal. Showers, lavatories, and sinks except for service sinks will be equipped with devices to limit maximum flow. Nonslip walking surfaces should be provided in showers and tubs.
Fixtures, where required, shall meet the requirements of the Uniform Federal Accessibility Standards (UFAS). Insulating trap kits shall be provided on all lavatories as required for disabled persons under UFAS.

Items should be selected which aid in the maintenance of the aseptic environment. Fixtures should be made of nonabsorptive, noncorrosive material. Items of equipment serviced by utility lines (air, gas, water, and the like) should be suitably valved so that each piece of equipment can be isolated without interruption of services to any other equipment.

Thermostatic mixing valves should be provided for hydrotherapy baths, x-ray processors, and other fixtures requiring controlled-temperature water supplies, if the equipment manufacturer does not supply a valve. Fixtures, devices, and equipment (autopsy tables, for example) must be installed to ensure no cross-connection between potable and nonpotable water supplies.

Shower walls and floors should be constructed of ceramic tile installed on a mortar bed. A maximum 15 mm lip will be permitted on showers. Temperature-regulating mixing valves with a pressure balancing and flow control device shall be provided for all showers.

All water closets shall be wall mounted with low consumption, 6 L per flush, of the siphon jet type. Blowout type closets are permitted in the lab side of the airlock for changing rooms in BSL-3 and BSL-4 laboratories. Water closet seats should be institutional weight of the openfront type, less cover, and furnished with heavy-duty stainless steel check hinges. Where flushometers are furnished with integral bedpan washers, the critical level of the flushometer vacuum breaker shall be a minimum of 150 mm above the full upright position of the bedpan spray arm.

All urinals should be wall mounted, 4 L per flush, low consumption, and of the siphon jet or blowout action type. Washout urinals must not be used.

Lavatories and Sinks: Wall-mounted lavatories shall be of vitreous china or stainless steel construction with an integral backsplash and should include concealed-type chair carriers. Counter-mounted lavatories should be constructed of enameled cast iron or stainless steel except where the fixture is integral to the countertop. Self-rimming and undermount lavatories should be bedded in sealant before the fixture is set.
Sinks should be selected for appropriate durability and corrosion resistance. The design engineer should consider the specific application and location of the fixture in assessing the need for Type 316 stainless steel. All stainless steel sinks shall be securely fastened to the countertop with mechanical-type fasteners. Snap clips must not be used.

Janitor mop sinks and service sinks should be constructed of enameled cast iron or stainless steel.

Water closets, urinals, and lavatories serving the employee food-service rest rooms shall be provided with electrically actuated and emergency power, hands-free sensor operation. In new construction, all lavatory faucets, urinals, and water closets in public rest rooms should be provided with hand-free hard-wired electric flushometers wired to emergency power. The sensor serving the fixture should be adjustable and shall be recessed in the wall behind the fixture. The sensor design should be adjustable and replaceable. Battery-operated fixtures must not be used.

Dedicated hand-washing sinks in commercial food production areas should have hand-free controls.

Specifically designed and manufactured carriers shall be provided for all wall-mounted fixtures. Pipe chases should be sized to accommodate carriers.

Bathtubs and Showers: Standard patient-room bathtubs at the NIH shall be constructed of enameled cast iron and shall include durable nonslip surfaces. Automatic actuated wastes shall be provided at tub waste outlets. Shower faucets shall be of the cycling-type valve, rotating through cold to the hot position with an ADA-compliant lever handle. Shower valves shall always be of the thermostatic type, except that in the case in which the supply to the shower is provided with hot-water over-temperature protection, pressure balance valves will be accepted. The limit stop on the shower faucet shall be set at 43 °C (110 °F) maximum. Faucet trim, levers, and escutcheons shall be constructed of stainless steel or chromeplated brass. Shower and tub faucets shall include integral check-stops. Reverse-core faucets should not be specified, such as those occasionally provided in back-to-back applications. Plumbing supplies at the NIH are to be roughed in properly, with hot water on the left and cold water on the right, as would apply during normal use of the fixture.

Faucets: Faucets shall be selected which are suitable for the appropriate application, and with special consideration of the need to maintain an aseptic environment. Only laminar flow-type, non-aerating stream faucets shall be utilized in clinical areas of NIH facilities. Aerating stream faucets are not utilized in BSL-3/BSL-4 spaces. All laboratory sink faucets shall be provided with integral vacuum breaker spouts.

Where foot pedal valves are desirable, units, which mount above the floor in casework with fold-up pedals, are preferred over on-floor mounting, because of increased sanitation. Piping should be concealed under casework so as not to preclude the use of cabinet space. Where faucets include both hand and foot pedal operations, separate isolation valves shall be provided for the foot pedal valve to facilitate maintenance.

Where two-handle wrist-blade faucets are required, ceramic-type faucet valving with brass or stainless steel internal components are preferred over other means of valve closure. It has been found that ceramic valve faucets maintain handle alignment and are less prone to leakage than compression valving. At the minimum, all faucets should include a fully renewable valving design to minimize potential leakage and simplify maintenance.

Faucet spout length and gooseneck size should always be carefully matched to the sink size. The A/E must coordinate with the user to determine the appropriate location for swing versus rigid fixed spouts.

Fixture Trim: Fixture stops serving lavatories, sinks, and similar fixtures shall incorporate threaded inlets. The use of compression fittings is generally undesirable; however, a single compression connection at the downstream side of the fixture stop may be provided, except for foot or knee pedal-operated valves. Fixture stops shall be of the heavy-duty commercial grade type and shall be the loose-key type in public areas.

Fixture Traps and Drains: Fixture traps, drains, and tailpieces shall be selected of corrosionresistant materials. Such trim for general sinks and lavatories shall be 17 gauge cast brass or stainless steel. An integral trap cleanout is not required because the trap can be easily removed without the increased potential for leakage of opening a cleanout built into the trap. Fixture drains, tailpieces, and traps on corrosion-resistant sinks, including sinks specified as Type 316, shall utilize stainless steel or other corrosion-resistant materials. Brass drains and traps are not utilized for fixtures fitted with high-purity water outlets, but, rather, stainless steel or corrosion-resistant piping materials to match the waste system are utilized.

The drain and trap connection to lab sinks, fume hoods, and similar equipment should be of the mechanical joint type, to permit removal for maintenance. All connections downstream of the laboratory fixture trap are as specified for laboratory waste systems.

It is important that fixture supplies be appropriately anchored to the building structure. The plumbing fixture or device must not carry or be required to support the piping installation.

The engineer should require plumbing services to fixtures to be roughed in properly so as to preclude requirements for exposed offsets of trap arms, extensions, or excessive tailpiece or fixture supply length. Improper rough-ins often result in leakage, maintenance, and aesthetic concerns. Each fixture and equipment must be provided with independent isolation valves or supply stops. It is imperative that facilities staff be able to service fixtures, faucets, and equipment without disrupting other areas of the facility.

Plumbing Fixtures Serving BSL-3 and BSL-4: Special attention is provided to the selection of plumbing fixtures serving BSL-3 and BSL-4 spaces. Sanitation and resistance to fouling, durability, and prevention of stoppages are of the utmost importance. Fixtures with concealed spaces are not permitted. Lavatories are specified without overflows because of the potential for these concealed spaces to harbor pathogens. Fixtures with integral trap seals (such as water closets) are selected to ensure sufficient trap seal depths, and minimize potential for stoppages. Stainless steel blowout fixtures with 100 mm deep trap seals are available, or manufacturer-modified blowout bowls are utilized as required. Flushometer selection must be appropriate to match the fixture design to ensure proper operation. Water closets and faucets are of the electronic, hands-free type, hard wired and on emergency power. Drinking fountains located outside labs are of the hands-free operation type, utilizing electronic sensors or knee actuation. Indirect waste receptors in labs are constructed of stainless steel or equivalent sanitary, chip-resistant materials compatible with the disinfectant process. All faucets in the lab are actuated by electronic hard-wired and on emergency power sensors, or knee actuation. Foot pedal valves are provided with slow-close valving, are utilized only where selected by the NIH in lieu of electronic or knee actuation, and are arranged to permit ready cleaning behind and under the device. Lab faucets are provided with specially designed vacuum breakers and are served by only the dedicated lab water distribution system.

Commissioning of Plumbing Fixtures: Proper adjustment and commissioning of plumbing fixtures, equipment, and appurtenances are vital to ensure proper operation, conservation of resources, and minimal maintenance. The engineer should specify that plumbing fixtures and faucets be properly commissioned. Flow rates, limit stops, temperature controls, and pressure regulators must all be adjusted for proper operation. Drinking fountains shall provide a sufficient stream at the bubbler to preclude contamination, without overshot or splashing. Water closet and urinal flushometers are adjusted for a proper and thorough flush. Automatic fixtures are adjusted for proper actuation and sensor range.

H.3.2 Water Supply Systems: The NIH obtains water from WSSC. The water is supplied through an underground grid network to the buildings. The water mains into the buildings serve the domestic potable water, the industrial nonpotable water, and the fire protection water system.

Each critical facility shall be provided with two water services, which shall be appropriately connected to the campus loop. Supply connections shall be to different mains/points on the NIH supply grid to ensure continued water supply. General lab facilities need not automatically be provided with two water supplies; however, the water service shall be double-fed. Proper backflow prevention devices shall be installed at the water service entering the building to separate the incoming water service into two distinct systems, one system being the building’s fire protection system, and the second system being the building’s domestic water. This arrangement shall protect the campus distribution system from backflow. Critical facilities may be provided with additional emergency water connection, isolated inside the building with a normally closed and locked shutoff valve and check valve, which shall terminate at an approved location. The emergency water connection shall be designed for use by a potable water tanker truck in the event of a catastrophic failure of the NIH/WSSC water supply. The emergency water connection shall connect to the water distribution system downstream of the main building domestic water service backflow preventer to eliminate any potential backflow to the incoming water supply.

Downstream of the building water service backflow preventers, additional backflow preventers shall be provided to isolate each subsystem (such as lab water system, mechanical water, etc.) This arrangement shall protect the building potable water system from backflow hazards. Except for those in BSL-3 and BSL-4 facilities, backflow preventers are generally not arranged in series because of increased pressure loss. Fire protection backflow preventers are not installed in series. In the case of BSL-4 lab water systems, the use of a break tank shall be considered.

The A/E shall determine the adequacy of the water pressure for the areas being designed. Water booster pump systems will generally be required at the NIH and shall be of not less than triplex design. Domestic water booster pumps shall be connected to emergency power. A minimum flowing (residual) water pressure of 276 kPa at the hydraulically remote fixture or equipment shall be provided. The system shall be sized to provide for both minimum flow requirements and maximum peak flow, with at least one redundant pump on standby. All pumps shall alternate in the appropriate lead-lag sequence, and include a pump exerciser function. Local control systems with system operating status and alarm condition readout are provided at the equipment. Remote signal to building automation system is generally limited to a general fault alarm for each system source. The use of an accumulator tank may be evaluated for non-clinical facilities but shall not be utilized in clinical applications because of the potential for bacterial growth. This minimum supply pressure is critical to proper fixture and equipment operation, especially with modern laboratory and hospital equipment and low-consumption water closets. It also minimizes the potential for a backflow condition.

A pressure-reducing valve assembly should be provided if required to limit the maximum water pressure to 552 kPa at any service outlet. A minimum of two pressure-reducing valves shall be provided in parallel, with a normally closed bypass. Pressure-reducing valves used for main system or pressure zone pressure control shall be of the pilot type, municipal grade, with stainless steel trim. The available water supply shall be analyzed on the basis of flow test data resultant of a proper hydrant flow test performed on the closest effective hydrant, performed in accordance with NFPA 291, during the design phase. All systems shall be designed a minimum of 10 percent below the water flow curve, but not less than a 34 kPa allowance for future demands on the supply main and to account for flow test accuracy. The engineer shall evaluate water supply source conditions at the time of flow test and make appropriate adjustment in calculations as required to account for seasonal system capacity fluctuations and similar conditions.
In the early design stages, a water supply distribution approach should be developed that meets all program requirements of the facility. Consideration should be given to the use of three different distribution systems to service domestic potable, industrial nonpotable, and mechanical systems. A laboratory reverse osmosis (RO) water system with local polishing equipment is frequently a fourth system and will be discussed hereinafter. Fire protection systems shall always be isolated via a separate feed from all other water systems. Comprehensive life-cycle costing that includes the installed and maintenance cost of backflow prevention devices should be performed to justify the design approach taken.

The three-system distribution approach has the items in Table H.3.2 connected to each system:

Table H.3.2 Three-System Distribution Approach

All laboratory water fittings should be equipped with vacuum breakers in addition to a backflow preventer installed on main. Smaller building projects, general use facilities, and renovation projects may not require the three-system distribution approach and shall be designed accordingly.
It is always preferable to install emergency eyewash and emergency shower fixtures only on the building potable water system, as mandated by code and ANSI standards. However, the engineer must take steps to prevent the stagnation of these systems that can occur from infrequent use. An independent loop, generally 50 mm in size, should be provided for each lab or lab floor as required within a building wing and should include an automatic purge sequence actuated by a timer or the building automation system. The piping loop shall be arranged to minimize the length of dead legs to individual fixtures, and the loop shall be set to fully purge once per week. Where necessary, a serpentine pipe arrangement may be provided. The piping loop shall be constructed only of copper piping materials.

In some buildings, the mechanical water system may not need to be extended throughout the entire facility. In such cases, hose bibs and wall hydrants may be connected to the domestic water system, when the hose bib or hydrant incorporates proper backflow protection devices. In the event of mechanical water usage only in remote locations within the building, mechanical equipment may connect to properly sized building domestic water piping when isolated from the potable water system with appropriate backflow preventers.

H.3.2.1 Pipe Sizing: Water piping systems shall be designed for minimal pressure drop and low velocity to limit noise generation and erosion corrosion. Pipe mains shall be designed for the maximum calculated flow at the design stage and to provide a 20 percent allowance for future expansion. The system distribution design shall utilize appropriate fixture unit values, with the cold water system mains, risers, and major branches sized on the basis of flushometer system curves. Hot water systems shall be sized on the basis of flush tank curves. Special demands shall be added directly to the calculated flow requirements, without diversity. Where a minor cold water branch line or runout serves only fixtures such as sinks, lavatories, and so on (no flushometers or high-use volume outlets on the line), the line may be sized on the basis of flush tank curves, providing it is still connected to a main line that is sized for flushometer and the complete required hydraulic design criteria are met, including velocity and pressure loss limitations. No building combined water service shall be less than 200 mm. With the exception of tempered water to multiple low-flow lavatory faucets served by a common thermostatic valve, a 50 mm supply shall not serve more than one fixture. Water pipe sizing shall generally conform to the requirements in Table H.3.2.1 below.

Table H.3.2.1 Pipe Sizing

The incoming water service shall be sized to incorporate the criteria of plumbing demand flow rate at a maximum velocity of 2.4 m/s, and total plumbing water demand plus fire system water demand at a maximum velocity of 4.9 m/s. The C-Factor used for the incoming water service calculations shall not exceed 120. Fire department hose stream allowances are added at the point where they occur, and plumbing design calculation requirements should be appropriately coordinated with the fire protection engineer.

The flow rate of the maximum design quantity of emergency showers and eyewashes shall be included in sizing of water system piping and equipment based on an appropriate quantity of emergency fixtures as compared to the actual quantity of fixtures, developed with input of the user. Emergency eyewash and emergency shower demand flow rate need not be added to the plumbing water demand for purposes of sizing the combined incoming water service when the incoming water service sizing includes all other plumbing and fire water demand.

The design demand of the largest, most demanding zone of lawn irrigation (or maximum flow of zones operating at one time) shall be included in the design calculations as plumbing demand. Likewise, any constant flow mechanical equipment or miscellaneous demands shall be included.

The engineer shall consider the unique demands and applications of plumbing systems at the NIH, when sizing systems using Hunter’s Curve methods and determining fixture units. Because of the size, application, and equipment used in NIH facilities, the engineer should thoroughly consider application of sizing methodologies to avoid drastic undersizing or oversizing.

H.3.2.2 Domestic Potable Cold Water: Domestic cold water should be connected to all general-use-type fixtures. Domestic cold water supplying drinking water, food processes, ice machines, and so on with water intended for human consumption must be protected from backflow from other systems in strict compliance with code requirements.

H.3.2.3 Domestic Potable Hot Water: Potable hot water is generated from the potable cold-water source using semi-instantaneous-type steam water heaters in most cases. Packaged electric or gas-fired heaters may be employed for small applications. Large storage tanks should be avoided because of the potential for bacterial growth. Water heaters should utilize a control arrangement listed for use in domestic hot water applications, which ensures accuracy over the entire flow range to within ±4 degrees. The preferred control valve for steam modulation is of the pneumatically actuated type. The engineer should consider the application of 1/3-2/3 control valves for central hot water production equipment. Double wall heaters shall be specified for potable water system applications. Heaters should generally be sized such that full demand may be met with any unit out of service. Steam supplies to the heaters are generally sized for full demand plus 20 percent allowance for future growth. The plumbing engineer shall consider the potential for Legionella in all large hot water distribution systems and shall select the most appropriate system in consultation with the NIH.

For most buildings at the NIH, hot water shall be heated to a temperature of 62 °C for distribution to kitchens and utility fixtures. The water shall be tempered down to 51 °C for general distribution with master thermostatic valves. Booster heaters at the kitchen or dishwasher shall provide 82 °C water for dishwasher final rinse locally. Undercounter-type dishwashers for break rooms and similar areas are provided with water supplies of not less than 60 °C for washing purposes. Hot water for commercial laundry purposes should generally be provided separately from the building system. Thermostatic type shower valves shall be selected, except that pressure-balance shower valves may be utilized where overtemperature protection is provided at the master mixing valve station as described below.

In the case of large facilities of multiple pressure zones, hot water may be generated and distributed at 62 °C, and local thermostatic valves shall be utilized at each pressure zone to reduce distribution temperature to 51 °C prior to reaching general fixture outlets. Thermostatic-type shower valves shall be selected, except that pressure-balance shower valves shall be accepted where over-temperature protection is provided at the master mixing valve as described below.

For clinical facilities housing nonambulatory patients at the NIH, two design methods shall be permitted, and each shall be evaluated during the preliminary design phase:

1. Separate hot water heaters shall be provided for food service and utility applications, consisting of hot water generated and distributed at 62 °C and boosted locally for dishwasher final rinse. A second complete hot water system to serve the patient areas shall be provided, with generation and distribution temperature of 46 °C. Shower faucets shall be of the thermostatic type. The patient system shall be provided with copper-silver ionization treatment equipment and appropriate monitoring.
   
   
2. For systems not provided with copper-silver ionization, hot water shall be generated and distributed at 62 °C. Hot water shall be tempered at the local pressure zone down to 46 °C. Over-temperature protection shall be provided downstream of each master mixing valve, as described below. Shower valve selection may be either the thermostatic or pressure-balance type.

Hot Water System Over-Temperature Protection: Protecting building occupants and patients from dangers of scalding is of primary importance at the NIH. However, as it becomes increasingly necessary to increase hot water production temperatures to minimize bacterial growth such as Legionella, the risk of scalding increases. Thermostatic mixing stations are the preferred method of temperature control prior to patient distribution and shower facilities; however, any mechanical device is prone to suffer failure or maladjustment. In addition, improper balancing and piping arrangements can cause temperature increases beyond the design operating temperature. Unless otherwise indicated above, fail-safe over-temperature protection shall be provided downstream of master mixing valve stations that serve nonthermostatic-type shower faucets or provide hot water supply to nonambulatory patient areas, anytime water is produced over 51 °C. The over-temperature device shall consist of a temperature transducer, solenoid valve, and alarm signal to BAS. The over-temperature protection device shall be arranged to isolate a single mixing valve assembly and alarm an over-temperature condition. A minimum of two thermostatic high-low systems shall be provided, each with its own over-temperature protection and each capable of maintaining at least 80 percent of the design peak flow at the design pressure drop, so as to ensure continued supply of hot water in the event an over-temperature condition activates shutdown of a single mixing valve assembly. Each sensing probe, outlet check valve, and the piping design at the mixing valve station shall be properly arranged to prevent actuation of both valves in the event of failure of only one device. All mixing valve assemblies shall be properly sized to effect proper temperature control under conditions of minimum flow.

Legionella Control Methods: Appropriate control measures for Legionella shall include consideration of copper-silver ionization equipment. Where utilized, copper-silver ionization treatment need not be provided with redundancy. The residual efficacy of copper-silver treatment has been shown to last for months after shutdown, thus affording ample time for any necessary maintenance.

While copper-silver ionization treatment will not generally be considered necessary for laboratory facilities where plumbing systems are properly designed, clinical facilities pose a higher risk due to the nature of occupants of the facility. It should be recognized that while Legionella is always a concern in water distribution systems, special consideration is given where the system is likely to be used by the elderly, those with respiratory ailments, and those with compromised immune systems. Aerosolization of water at showerheads is of special concern in such facilities.

Alternative control methods are generally not considered advantageous where it is determined that Legionella precautions are warranted. Chlorinization and UV sterilization methods are undesirable because of ineffectiveness against biofilm and sediment formation in piping systems that harbor and shield the bacteria. Effective chlorinization levels also severely increase piping corrosion. As Legionella thrive at temperatures below 57 °C, temperatures necessary to effect proper sterilization pose risk of scalding to building occupants and can be of only limited effect because of uncirculated portions of the system, sediment, and biofilm.

The A/E designs piping systems to minimize uncirculated hot water branches and should avoid the use of natural rubber gaskets, seals, and components, which often serve as nutrient to the bacteria. Cold water systems should be kept cold and away from heat sources, and large water storage tanks, which promote stagnation, should generally be avoided. Copper is the preferred piping material where feasible.

Temperature Control Adjustment: Limit stops and controls on showers and faucets shall be adjusted to limit the maximum hot water temperature to 43 °C at patient showers, and 49 °C maximum hot water temperature shall be provided at general sinks. Water at 60 °C shall be provided to serve kitchen areas, sinks, or where otherwise required for proper use and operation. Hand sinks in kitchens shall be provided with local thermostatic valves below the fixture to limit hot water to 49 °C, or provide tempered water at 39 °C for sensor-actuated faucets. Thermostatic protection shall be provided and set for a maximum of 38 °C for faucets and 40 °C for showers in children’s wards or areas likely to serve children.

Limit stops at lavatory faucets in public toilet rooms must limit maximum hot water temperature to 43 °C. Where automatic faucets or wrist blade faucets are utilized, a local thermostatic valve may be provided.

H.3.2.4 Domestic and Industrial Hot Water Systems Recirculation: Recirculating systems are designed specifically for each application to maintain the required hot water system temperature. The required recirculation rate is calculated for each loop and sized to offset system heat losses. The A/E should indicate the required flow rates for each circuit on the design drawings. Rule-of-thumb recirculation system sizing is undesirable, as system sizing is often inaccurate and results in a waste of energy or inadequate flow. It is preferable to calculate heat loss on the basis of system operating temperature, ambient temperature, and insulation value. For most interior building installations, the engineer should consider the use of an 18 °C ambient temperature condition in sizing calculations. A parallel hot water return should generally be provided alongside hot water supply mains and risers. Each hot water supply branch should be recirculated back to the hot water return and fitted with an appropriate balancing device, as required to maintain hot water to fixtures within the recommended time criteria as outlined by ASPE. In general, circulated hot water lines should not exceed 7.6 m in developed length. The engineer should consider the effect of large diameter branch takeoffs from mains serving low-flow volume fixture outlets. The outlet flow rate of the fixture must be considered when evaluating how close to the fixture the recirculation loop may terminate.

Serpentine-type hot water distribution, or the arrangement of hot water recirculation in a single supply loop with the return taken only at the end of the fixture supply loop, is undesirable, as these systems do not offer flexibility for renovations or fixture additions. By providing a parallel or centrally located hot water return, each supply branch may be recirculated independently, and additions and renovations may effectively be connected to the common return without disrupting building function. Hot water return rate for each riser should be carried by a balancing station at the top of the riser where the supply riser loops back to the return riser. In this way, the hot water return on each floor need only be sized for the flow rate required to serve that floor, and the renovation of an area of the building is less likely to affect other areas.

Improper adjustment of hot water balancing valves can quickly throw an entire hot water system off balance. To help minimize these risks, the main hot water return from each floor should be provided with a “floor balancing station,” even where local circuits are individually balanced. A thermometer should be included at the end of each floor’s hot water return connection to the riser. Automatic balancing valves are generally undesirable due to inflexibility for changes in system flow rates that can be required during a renovation or revision in design.

In general, hot water supply to kitchens and cagewash areas should be sized for an approximate 5 °F temperature differential. General building areas should be sized for a 7 °F differential, except that higher differentials (up to 15°) may be used where justified by the specific application. A/Es should be cognizant of the required pressure differential to properly adjust balancing valves. In general, at least 0.06 L/s is required with a 15 mm pipe size. Engineers may consider reduced size balancing valves on larger diameter returns, where justified by the required flow rate and provided within acceptable velocity limitations.

Legionella provisions are not generally required with industrial hot water systems. Hot water is generally produced at 51 °C and directly distributed. In some cases, 62 °C distribution is desired because of laboratory equipment operation requirements. Over-temperature shutdown protection is not required in industrial hot water systems. Similarly, master thermostatic mixing stations are generally not required, unless hot water is from a source above 62 °C. Animal research facility cagewash is generally provided with independent water heaters, served from the industrial cold water system.

H.3.2.5 Industrial Nonpotable Water: System features may be similar in many respects to the domestic systems, but the two must be totally isolated. All laboratory, animal research facility, and process equipment and fixtures should be connected to the industrial water system. Separate cold, hot, and recirculating water mains and water heaters, tempering valves, and so on shall be provided.

Industrial water system sizing is driven by user requirements, which are normally difficult to define. The A/E shall establish through extensive consultation with researchers the design criteria for each type of space so that the utility services are delivered in sufficient quantity and pressure to meet current and future requirements. Design criteria shall be documented and approved early in the design stages.

H.3.2.6 Mechanical Water: The mechanical water system is limited to a cold water source that provides makeup for building HVAC systems, backup for cooling water systems, routine maintenance cleaning, and watering. Sizing is based on initial or quick-fill requirements and design flows for backup conditions.

Hose bibs shall be provided within the building equipment room for cleaning and within planters for watering. Wall or yard hydrants shall be provided outside the building to accommodate landscape watering, pavement/sidewalk cleaning, and loading dock cleanup.

H.3.2.7 General Water Distribution: General water systems distribution should consist of a double-fed horizontal loop, with separate risers serving each end of the loop. Large facilities consisting of multiple building wings are provided with independent fully sized risers for each building wing, except that the redundant riser may serve multiple wings where beneficial and located in a common area. Systems are designed to permit bidirectional flow, with valving and thrust restraints designed to function properly with flow in either direction as might occur during isolation of a water service or riser.

Services to each floor of a building wing are connected to respective supply risers, independent of other floors, to minimize potential disruptions during service and future renovations.

Shock absorbers are provided at equipment with solenoid valves and quick-closing valves, and at other potential water hammer sources. Air chambers should not be permitted in lieu of manufactured water hammer arrestors, as such devices are prone to stagnation and quickly lose their air charge.

Mixing valves (including devices located at fixtures), which present a constant open path for flow of hot and cold cross-flow, can provide numerous problems in any large water system. It is necessary that wherever these devices are required, whether of the thermostatic type or simple mechanical mixers, check valves must always be provided to prevent cross-flow. The design engineer should be careful to specify durable mixing valves, which utilize only check devices constructed of brass or stainless steel components. Mechanical mixing valves below lavatories can be especially problematic when care is not taken in the specification of the product. Many of these devices utilize frail plastic or rubber seals, which quickly fail. In such cases, the provision of secondary in-line check valves should be considered. While single-control faucets do not generally require check valves because they are not generally open for extended duration and when in use are usually at the terminal end of an open system, shower faucets, therapy tubs, and hose stations should always be provided with swing check valves or integral checks on both the hot water and cold water supply inlets.

The A/E should avoid locating cold water pipes immediately adjacent to steam lines and external heat sources. It is important that cold water systems not be permitted to warm, not only to avoid potential for bacterial growth, but also to ensure adequacy for the user.

Particular attention must be given to proper dielectric protection between differing metals. The use of dielectric flanges and appropriate waterways is preferred. Brass components should not be used as the sole isolating means between copper and iron piping systems.

Provision of adequate valving is of the utmost importance at the NIH. Valves should be provided in such a manner as to facilitate maintenance with minimal disruption and to isolate systems for renovations and unexpected emergencies. It is well recognized that one of the single greatest reasons for loss of operation of a facility after a catastrophic disaster is water damage and loss of water supply attributable to inadequate valving. Valves should be provided at the base of each riser, at each riser connection, at branch piping to fixture groups, and at fixtures and equipment requiring maintenance. Each floor distribution loop should be provided with sectionalizing valves, such that a fixture branch or portion of the loop may be shut down without disrupting the service to the entire floor or major portion of the supply loop. Valves should be arranged to permit isolation of specific areas without affecting operation of adjacent spaces. All valves should be arranged in an accessible manner. Where valves are located above ceilings, thorough coordination of piping services shall be required to ensure proper access for valve operation. Drains should be provided at the base of all risers and should be furnished with a ball valve, NPT threads, and a removable cap. For riser sizes 50 mm and smaller, a 20 mm hose valve may be provided with a cap but must include a vacuum breaker if serving a potable water system.
The engineer must avoid routing piping concealed above ceilings or burying it under slabs below major electrical or data communications equipment areas. Piping should not be located above panel boards or switches, including the required service areas for this equipment.

Provision of pressure gauges at floor takeoffs from major risers assists NIH maintenance with systems troubleshooting.

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H.4 Sanitary and Waste System

Sanitary, waste, and vent systems shall meet the requirements of WSSC. Each plumbing fixture or drain shall be trapped and vented in accordance with code requirements. Vent systems serving plumbing systems are of the conventional through-the-roof type. Mechanical vent devices, stack aerator and de-aerator systems, and other nonconventional systems are not utilized. The sizing and pitch of drainage piping shall be per code and the requirements described in this section.

For general sanitary drainage applications, drain piping can be cast-iron hub and spigot for underground piping and hubless cast iron for above-ground piping. For laboratories intended for research in biology and chemistry or other research where concentrated acids or bases may be accidentally or improperly discharged into the drainage system, or for laboratories and cage wash facilities in which chemicals will be used, chemical-resistant piping and vent material should be considered. Drains receiving high-purity water discharge, such as lab sinks adjacent to water polishers, and drains at dialysis and pure water production equipment shall be of corrosion-resistant materials. Piping, materials, and joint methods shall comply with Table F.6. Such drain systems shall empty in neutralization systems prior to their discharge into the public sewer. The neutralization system shall be adequate to provide the proper pH discharge in accordance with WSSC discharge regulations. Vent piping material shall be as specified in Table F.6 in General Design Guidelines, Section: Mechanical. Vent piping serving drains that are made of corrosionresistant materials selected for kitchens and similar applications may be sanitary vent piping materials as indicated in Table F.6 in General Design Guidelines, Section: Mechanical. Vent piping serving oil interceptors and similar combustible systems shall be approved metallic materials only. While pH treatment shall not be automatically provided for all facilities, the engineer must consider not only discharge regulations of WSSC from the entire NIH campus but also the need to protect the longevity of NIH private sewer collection mains and lateral infrastructure.
Laboratory acid, animal research facility, or other special waste and vent systems shall be separate from the general use sanitary system. Grease waste systems should be routed through an appropriate grease interceptor, prior to connecting to the sanitary sewer. The effluent from the buildings shall meet WSSC requirements. Effluent with the following basic characteristics shall be excluded from the sanitary sewer system:

• Unmetered water such as air-conditioning condensate, stormwater, ground water, etc. except as allowed per the code
• Any liquid or vapor having a temperature higher than 60 °C
• Any water or waste containing grease or oil or other substance that will solidify or become viscous at temperatures between 0 °C and 60 °C
• Any waters or wastes having a pH lower than 5.5 or higher than 9.0, or having any other corrosive property capable of causing damage or hazard to structures, equipment, or personnel of the interceptor, other sewage-handling and transporting facilities, or other treatment works

The public and private onsite sanitary sewer systems shall be protected against the potential discharge of grease and oil originating from food-handling and related establishments.

H.4.1 General Drainage Design Considerations: Sanitary waste systems should be designed to maintain a minimum velocity of 0.61 m/s, and 0.91 m/s where possible. Special attention is given to the design of sanitary waste systems serving low-consumption water closets as well as systems transporting wastes that increase potential for pipeline stoppages. Systems should be hydraulically designed to minimize potential for stoppages and backflow of wastes or suds and to ensure provisions for maintenance. Horizontal waste branches should generally not be sloped less than 2 percent and often require slopes in the range of 3 percent, to aid in solid waste transport. Excessive slopes beyond 5 percent and less than 45 degrees are generally undesirable because of the potential for liquids to run off, leaving solids behind to accumulate in piping. Slopes of 1 percent and less should generally be avoided in piping sizes 150 mm and less. The A/E should also recognize the negative effects caused by oversizing or undersizing of horizontal waste piping systems. Drains and traps serving floor drains, floor sinks, and janitor service sinks should not be less than 75 mm diameter, regardless of anticipated usage. Individual showers and tubs should be provided with 50 mm diameter traps and waste. Floor drains and floor sinks in kitchens should be provided with drains and traps, which are 75 mm diameter, except that 100 mm diameter outlets should be used for the grease waste system. The use of horizontal waste piping less than 50 mm should generally be limited to trap arms serving lavatories and similar fixtures. The A/E should consider arranging fixture connections to provide “trail flows” to enhance drain line carry.

Waste piping systems should be designed and installed in a direct manner, with minimal horizontal offsets, to aid in the efficient transport of wastes. Piping mains located above ceilings should generally parallel the building construction and should generally not transverse building spaces diagonally. Long-radius fittings should be specified for horizontal-to-horizontal and vertical-to-horizontal direction changes. Double wyes should be avoided in the horizontal position, as it is not possible to maintain uniform slope in both directions and opposing branch inlets can result in separation of solids from the waste stream. Sanitary tee fittings should not be installed on their side or on their back as a waste fitting or to serve as a connection of a vent to a waste pipe because of the potential for stoppage. Sanitary crosses should be avoided in drainage systems. Specially manufactured double-fixture fittings should be specified for back-to-back or side-by-side fixtures discharging to the same vertical waste. The engineer should specify that piping be installed in proper alignment, with attention to joint quality, square cutting of piping, and proper insertion of piping into fitting sockets. Connections of individually vented fixture branches to horizontal mains should be through rolling offsets at a 45 degree position above the horizontal centerline, to minimize disruption to waste and air flows and minimize negative effects on solids transport. Such connection methods are noted on drawings or in
specifications.

With the exception of stacked major toilet rooms, waste and vent stack locations and horizontal distribution of piping should be independent for each building wing to minimize potential disruption during future renovations. Vertical waste stacks that transverse multiple stories should not be placed directly behind fixtures, but rather in dedicated permanent utility shafts and appropriate building columns. The A/E should always consider the potential for any one floor to be renovated in the future without causing excessive disruption on adjacent floors or necessitating future vertical stack offsets. The engineer must avoid routing piping in ceilings above or burying it under slabs below major electrical or data communications equipment areas. Piping should not be located above panel boards or switches, including the required service areas for this equipment. The engineer should consider potential disruption, which could result if the need to access lines for repair or renovation were to be required.
Vertical stacks and vents should be located at permanent chases and building columns rather than in partitions. Every attempt should be made to design stacks in a straight vertical configuration and to utilize offsets of not greater than 45 degrees from vertical where possible. Waste and vent piping stacks that transverse multiple floors of the building should not be located in interior portions. These create significant issues during future renovations and often result in excessive offsets, the need for relief venting, and excessive disruption to adjacent spaces.

The routing of waste piping above food service areas, surgery areas, and similar areas of special health concern is particularly undesirable and should be avoided as much as possible. However, where installation is unavoidable, specific safeguards should be provided to maintain sanitation for these areas. The use of fixtures with waste discharge above the floor is especially desirable, as well as the use of double-contained waste piping as indicated in Table F.6 in General Design Guidelines, Section: Mechanical. Drain pans, heavy-duty couplings, and similar items should not be considered equivalent to the safety provided by a leak-tight double-contained waste system over critical areas.

Where possible, branch lines serving food service areas should connect to the building drain independently of other areas of the building. This reduces potential for waste stoppages in main lines to back up into sanitary kitchen areas. Independent grease waste systems should be provided as described below.

Vent systems should slope upwards toward the roof terminal, and dry vents should not offset horizontally below the flood level rim of the highest fixture on the floor connected to the system, and generally not less than 965 mm above the floor. This helps to ensure proper circulation in the vent system and minimizes potential for blocked vents or backflow of waste into vent systems and the resulting septic line conditions. Vents should not be located within 7.6 m of any air intake or window, or in such proximity to any building opening or occupied area to be infiltrated by sewer gas or vapors. Vents should be adequately separated from sources of positive or negative pressure, fans, and so on to maintain atmospheric pressure within the venting system. Interceptors are designed to prevent air locking and sometimes require an independent local vent, acid, or sanitary vent, based on the application and design.

Careful consideration given to the arrangement of cleanouts during system design can greatly aid in increasing sanitation. Opening of cleanouts serving plugged waste lines, as well as the drain cleaning process itself, often results in unsanitary conditions caused by splattering and spilling wastes. Thoughtful consideration during the system design can help the NIH achieve increased building sanitation and reduce maintenance burden. For example, by providing two-way directional cleanouts at the exterior of the building, many main sewage stoppages can be cleared without even entering the facility. A separate entry to permit directed rodding upstream or downstream of flow should always be provided to permit control of the cleaning process. Such cleanouts should also be considered at other locations where beneficial to permit stoppages to be cleared without entering critical sanitary areas of the facility. Two-way cleanouts should not be provided in lieu of cleanouts at the upstream end of horizontal mains, but rather as a supplement to enhance the system. In many cases, horizontal piping in ceilings can be served by a wall cleanout located in a bathroom or similar readily washable area that discharges to the horizontal main. This can be a great advantage to the NIH, as the opening of a plugged water-filled waste line above finished ceilings is generally undesirable. Cleanout locations in biological waste systems must be carefully considered to avoid compromising the containment barrier. Cleanouts shall be provided as required by code, including at the base of waste stacks, and should also be provided as required to serve upstream ends of horizontal drains. The removal of a fixture such as water closet or urinal is an undesirable method of clearing drains and should not be considered equivalent to provision of adequate cleanouts. Full-size cleanouts should be provided for all waste lines up to 150 mm in diameter, and not less than 150 mm diameter for sizes above 150 mm. Wall cleanouts should be specified with appropriate plugs, and tapping of plugs directly into the waste or vent stack must be discouraged because of the potential for stoppages and exfiltration of sewer gas. The numerous piping systems at the NIH can often make it difficult or time consuming for facility personnel to locate proper cleanouts to service systems. Each floor cleanout cover should be stamped to indicate the system served. Laboratory and acid waste is designated “AW.” Sanitary waste is designated “SAN.” Storm drainage is designated “SD” or “STORM.” Grease waste is designated “GW.” The A/E recognizes that provision of adequate cleanouts is merely providing access for clearing stoppages and does not supersede thoughtful system design.

The engineer should carefully consider pipe material selections serving autoclaves and high-temperature wastes. Materials such as borosilicate glass and high-silicon iron should be utilized, rather than plastic piping materials. Where waste is non-corrosive, cast iron with hubless, caulked, or compression gaskets may be specified. Normal autoclave waste is not corrosive and may be routed to either the sanitary or the laboratory waste system. However, where autoclaves include a high-purity water rinse, the connection should always be to the lab waste system, because of the corrosive nature of high-purity water. Careful consideration should be given to the specification of joint connections between floor sinks and floor drains and the selected piping material, and to the potential for expansion and contraction. Some piping materials, such as high-silicon iron, are not of iron-pipe-size external diameter and often require special connections to drains and floor sinks. Where serving autoclaves, a flanged mechanical joint adapter with a Teflon flange gasket connecting to a flanged stainless steel floor sink outlet is often the most appropriate way to address material transition and potential high-temperature waste.

It is especially important that the engineer specify proper backfill and excavation methods. Piping that loses proper slope or alignment because of improper bedding and backfill not only increases potential for stoppages but also can result in leakage underground and broken lines. The quality of the underground system design layout and installation often sets precedence for the durability and maintenance requirements of the entire system.

H.4.1.1 Gravity Drainage and Backflow of Waste: Drainage systems should be designed to flow by gravity wherever possible. The use of pumping systems should be avoided, except where absolutely necessary. Where pumped systems are required, equipment is of the duplex type, each capable of discharging 100 percent of the incoming peak flow in the event of a pump failure. Building areas that are sufficiently elevated above the sewer to not require discharge through a pumping system should be routed independently to discharge by gravity.

The plumbing engineer should arrange plumbing systems such that a stoppage in the exterior sewer will not result in sewage backflow into the building, but rather will be relieved outside the building by manhole covers. Backwater valves should be provided outside the building for any drainage main that serves fixtures or equipment whose flood level rim is not at least 2 286 mm above the elevation of the manhole cover serving the system, or above the next upstream manhole. In order to protect lower level fixtures from serving as a relief point for upper level fixtures in the event of a building drain stoppage, and also to permit gravity drainage without resistance of the backwater valve, all drains with flood level rim elevations above the above reference point shall not be combined with lower level mains upstream of the backwater valve. The backwater valve shall be located at the connection with the manhole, or with similar accessible means, to permit access for sewer rodding, or other service. Sufficient venting shall be provided to serve the building sewer either through stacks that do not discharge through the backwater valve or by provision of a relief vent. The use of individual backwater valves is an undesirable practice because of restrictions in the inlet capacity and potential for fouling.

H.4.1.2. Indirect Waste: Indirect waste connections are provided for all plumbing fixtures or equipment that is of public health concern. Food preparation, dishwashing, and warewashing equipment, autoclaves, ice machines, and similar equipment discharge with an appropriate air gap to an approved indirect waste receptor. An air break may be utilized for items such as photo equipment and nonpotable equipment discharge, where an indirect connection is required, but a full air gap is not needed.

In general, stainless steel floor sinks are the indirect receptor of choice and should be selected for appropriate capacity and with the proper part grate design to eliminate splashing. An internal dome strainer or sediment bucket should always be provided. Stainless steel receptors provide enhanced cleanliness and corrosion resistance and are not susceptible to the chipping of enameling common to enameled cast iron, which often results from foot and wheel traffic, as well as during cleaning and replacement of sediment buckets. However, cast-iron floor sinks are well suited for installation in mechanical rooms and similar unfinished areas. Floor drains with funnel tops may be utilized for limited flow applications, such as from ice machines. Floor drains and floor sinks should always be installed with their top grate flush to 0.31 mm below the finished floor, with the finished floor slightly tapered to drain toward the receptor. The installation of floor sinks with rims installed above the floor is an undesirable practice that conflicts with the intended design of the fixture. Unsanitary conditions are created by unfinished surfaces and the ledge created when such devices are installed with rims above the floor. In addition, water, waste, and filth often accumulate under such conditions and can be difficult to clean. The only time waste receptors should be installed with rims above the floor is where specifically necessary to preclude floor drainage from entering the system, such as where a receptor is installed to direct clear water waste to the storm system. Indirect waste should generally not terminate at other plumbing fixtures, including janitor mop sinks, but rather to the appropriate waste receptor. Routing of indirect waste to janitor service sinks can result in flooding and water damage in the event a mop or bucket is left inside the sink blocking the fixture drain. While indirect waste from lab equipment sometimes drips into lab sinks, indirect waste must never terminate over culinary plumbing fixtures or similar applications where use or sanitation is impinged in any manner.

The use of hub drains and standpipe receptors is generally undesirable in finished areas because of the potential for trash and debris to enter the drainage system, as well as their unsanitary nature. The interior of these devices is not readily cleanable, and projections above the floor present both sanitation and safety hazards. Such devices, however, may be appropriate in certain mechanical room applications, as well as when connected to wall waste outlet boxes. In no case will any standpipe receptor be less than 50 mm in diameter.

Indirect waste receptors must always be installed in readily accessible spaces and must not be located in toilet rooms, casework, closets, or concealed spaces. In locating floor sinks and other indirect waste receptors, the A/E considers the potential for a waste line stoppage to result in overflow at the fixture and ensures the location permits cleanup and is not likely to cause damage to the building. The location must permit removal and cleaning of the sediment bucket or dome strainer and cleaning and mechanical rodding of the device in the event of a stoppage. Waste receptors of sufficient depth should be selected to prevent splashing and accommodate peak discharge conditions. Food waste disposers and similar equipment shall not be permitted to discharge through indirect waste receptors, but rather must be directly connected to the sanitary drainage system. As with other drainage systems, the A/E should be careful to specify floor sink and floor drain outlet connections that are compatible with the selected grease waste piping material.

The use of indirect waste piping less than 25 mm in diameter should be avoided for airconditioning condensate and food service applications, and this should be appropriately coordinated with food service consultants. Indirect waste lines less than 25 mm diameter are extremely difficult to maintain and frequently plug from sediment buildup. Plumbing connections to food service equipment should be included in plumbing documentation, after coordination with the food service consultant. The A/E must carefully evaluate food service equipment drawings and equipment installation requirements and should not rely on directions of food service consultants alone to ensure a code-compliant, well-designed system.

H.4.2 Laboratory Waste: The design engineer should carefully evaluate sizing of laboratory waste systems. Many items of equipment do not directly correspond to flow rates and values of common Hunter’s Curve fixture unit tables, as the tables were generally based around flow discharge characteristics of domestic plumbing fixtures and water closets. Cage and tunnel washers and similar equipment can generate particularly high peak flows and often produce suds-laden wastes. Diligence should be provided to validate system sizing for proper operation and for consideration of waste stack arrangement, segregation of wastes, and appropriate relief venting to prevent backflow.

In many cases in existing buildings at the NIH, horizontal waste piping must be offset excessively in walls during renovations to permit distribution in walls without disrupting floors below. The need for adequate cleanouts and sufficient pipe slope is especially important in such cases to facilitate and minimize maintenance.

The A/E should be careful to specify floor sink and floor drain outlet connection methods that are compatible with the selected lab waste piping material and system application. Often materials are specified with incompatible outlets, resulting in excessive delays and improper connections.

Laboratory waste should generally be provided in accordance with the general drainage design considerations above. However, in lieu of installation of cleanouts at every 90 degree horizontal change of direction, cleanouts may be provided at the upstream ends of horizontal branches, and at every 135 degree aggregate horizontal change of direction in the waste piping, with the maximum distance between cleanouts not to exceed 30.48 m.

The A/E should be sure to specify mechanical joint traps under lab sinks and fume hoods to permit removal for maintenance. Borosilicate glass piping is not utilized directly connected to darkrooms because of the potential for light transfer. It is also not utilized for vent penetrations through the roof.

pH treatment systems are not automatically installed at all laboratories, but rather are considered after analysis of the research process. Where pH adjustment systems are utilized, the A/E will consider the type of effluent to be treated. Treatment systems relying on limestone or marble chips are ineffective for alkaline waste streams and must be protected from solids in the waste stream. Solids tend to coat the neutralizing media and therefore render the system inactive. Even where solids interceptors are provided, the cleaning and disposal of such solids are subject to strict disposal guidelines, require extensive maintenance, and as such an application of such systems should be carefully evaluated. For these reasons, passive-type systems are not generally recommended for facilities with cagewash or slurry or solids in the waste stream.

An active neutralization system that utilizes sulphuric acid or carbon dioxide, and sodium hydroxide, the engineer should evaluate whether the batch-type, or continuous flowthrough, system is desirable. Waste streams with solid matter are better suited to the batchtype process, and the system should be especially designed to handle and flush all solids.

Lab waste treatment systems should be carefully sized to the system demand. Most lab waste streams are effectively treated in a very short time, and thus excessive retention times are generally not required when using active systems. All systems must be designed to allow continuous operation during service, and therefore pH monitors and similar controls should not be located inside the tank. The engineer should specify quality pH monitors and components. Systems should utilize sufficiently sophisticated controls to match chemical injection to the influent requirements and influent and effluent characteristics. Continuous flow-through systems should include controls to permit limited retention in the event of a spike in the pH of the influent stream. Batch-type systems should default to continuous flowthrough mode in the event a batch tank is removed for service. Constant-feed chemical injection systems are not acceptable. The A/E must carefully coordinate utility requirements for peak and normal flow rates of pH treatment systems with the civil engineer/site infrastructure.

H.4.3 Grease Waste: Dedicated grease waste systems should serve commercial food service areas of the facility, with venting and cleanout provisions as indicated above for sanitary waste systems. The grease waste system should be independent of other waste systems and should generally route grease waste to a properly designed exterior grease interceptor, prior to discharge to the sanitary sewer. All food service fixtures and equipment that provide a likely point of introduction of greasy wastes are directed to the grease waste system. Pot sinks, kitchen area floor drains and trench drains serving food service equipment (such as soup kettles etc.), the wash compartment of commercial dishwashers, hood wash, and similar connections are all directed to the grease waste system. Mop sinks, toilet rooms, food waste disposers, vegetable prep sinks, ice machines, and similar fixtures that generate sanitary wastes, excessive solid matter, or cold water wastes shall not discharge to the grease waste system. For large commercial dishwashers, it is often advantageous to route the final rinse compartment drain to the sanitary system by providing a separate floor sink. Water above 60 °C should generally not be routed through the grease interceptor. The A/E should work with the food service equipment specifier to coordinate separation of the final rinse compartment drain for routing to a separate floor sink or to ensure that an appropriate backflow-protected waste water cooling device is included in the dishwasher specification at the final rinse cycle, to limit waste water discharge to 60 °C.

The application of point-of-use grease traps is generally undesirable, because of the need for continuous maintenance and the unsanitary conditions that occur during servicing. These devices generally have limits to capacity and are inappropriate for use in serving an entire kitchen. However, for limited applications, such as where a single-wash sink is provided as part of a limited remote area, these devices can be beneficial. Grease traps should not be located in the food preparation areas of kitchens or other areas of public health concern. The application of grease recovery devices is sometimes advantageous; however, as with the application of grease traps, the A/E shall carefully consider the needs of the entire kitchen, floor drains, and floor sinks, which often contribute significantly to grease waste load and cannot be appropriately connected to this type of fixture.

The A/E must recognize the excessive potential for stoppages in the grease waste system and design carefully to both minimize stoppages and permit maintenance. The drainage design should produce a minimum velocity of 0.91 m/s, and 1.2 m/s where possible. Adequate cleanouts and direct pipe routing with minimal horizontal offsets are desirable. As with sanitary piping, the use of two 45 degree ells is often preferred to 90 degree horizontal directional changes. It is desirable to prevent the solidification of grease in the piping system, and therefore ice machine waste and cold condensate should never be routed to the grease waste system. It is always desirable to locate the grease interceptor as close as possible to the kitchen; however, the interceptor must be located exterior of the building and in an area accessible to the pump truck. Generally, interceptors should be located not more than 15-23 m from a location where the pump truck is planned to be during the cleaning process, and preferably as close as possible. The location of the grease interceptor is coordinated during preliminary design phases and should generally be in a service area, away from the public. In cases where the grease interceptor must unavoidably be excessively remote from the kitchen, the A/E should consider the application of industrialgrade electric heat tracing and insulation to the grease waste piping. In cases where the piping must be installed below ground, the heat tracing must be located in a stainless steel conduit, with sufficient pull boxes/junction boxes and eyelets to permit replacement. The A/E must also carefully consider proper protection of the piping and conduit from corrosion, and generally Teflon spacers and poured-in-place corrosion-inhibiting insulation materials are
effective. Because high waste line velocities are desirable to enhance waste transport, the grease interceptor inlet and system design must be carefully designed to reduce velocities and provide sufficient holding period for separation and eliminate short-circuiting. Grease interceptors should be sized to provide sufficient retention based on the peak inflow rate, velocity, and types of influent to be treated. A minimum of two compartments is desirable. Generally, a minimum 30 minute retention time is appropriate. Grease interceptors shall not require cleaning more than once per month. Two-way directional cleanouts should be provided at both the inlet and outlet of grease interceptors. The sanitary vent downstream of the interceptor should connect directly to the vertical cleanout riser with a wye-type fitting to minimize potential for stoppage of the vent. The tank vent and sanitary vent should not be combined until at least 965 mm above the finished floor and should be fitted with cleanouts. Interceptors at the NIH are provided with internal ladders with nonslip rungs.

H.4.3.1 Trap Seal Maintenance: Floor drains, floor sinks, and indirect waste receptors often provide a path for sewer gas to enter the building as a result of evaporation of trap seals due to infrequent use. The A/E shall carefully consider the potential for trap seal evaporation and provide automatic trap seal primers to replenish trap seals where necessary. Only electric-type, time clock-actuated trap primers may be utilized. Nonelectric- type pressure drop trap primers have proven unreliable and often malfunction from common pipeline debris or cycle excessively, resulting in excessive maintenance, water waste, and sewer gas infiltration. Providing a faucet near an indirect waste receptor is not considered an acceptable means of ensuring trap seal maintenance because of the constant manual intervention required. Floor sinks serving plumbing fixtures generally do not require external trap seal maintenance; however, indirect waste receptors serving mechanical equipment should be carefully evaluated to ensure adequate flow. Floor drains in toilet rooms and mechanical rooms should always be provided with automatic trap seal maintenance.

H.4.4 Biowaste Systems: Careful consideration is applied to the design of bio-waste syst