5.24 Plumbing Systems

Water conservation shall be a requirement of all plumbing systems. Use water-saving plumbing fixtures.

Domestic Water Supply Systems
Cold Water Service. Cold water service shall consist of a pressurized piping distribution system incorporating a separate supply line from the tap in the existing outside water main to the equipment area inside the building.

Water service shall be metered inside the building by meters furnished by the local department of public works. Incoming service shall have double check valves. Remote reading of meters will be accomplished by special equipment over telephone lines. Irrigation systems must be sub-metered for deduct billing of the sewer system.

Internal distribution shall consist of a piping system that will supply domestic cold water to all necessary plumbing fixtures, water heaters and all mechanical make-up water needs.

Distribution system shall include equipment that will maintain adequate pressure and flow in all parts of the system in accordance with GSA Facilities Standards.

Triplex booster pumping system shall be utilized if the water pressure is not adequate to provide sufficient pressure at highest, most remote fixture. The water pressure at the fixture shall be in accordance with the International Plumbing Code.

Hot Water Service. Hot water shall be generated by heaters utilizing natural gas, electricity or steam as an energy source. Selection shall be supported by an economic evaluation incorporating first cost, operating costs and life cycle costs in conjunction with the HVAC energy provisions.

Instantaneous hot water heaters are not permitted as a primary source. Domestic hot water supply temperature shall be generated at 60°C (140°F), and shall be tempered to 49°C (120°F) using a three-way mixing valve, before supplying to all plumbing fixtures. Hot water supply to dishwashers shall be at 82°C (180°F), and the temperature shall be boosted from 60°C (140ºF) to 82°C (180°F). Heat pump hot water heaters shall be used where possible to save energy. For incidental use, the use of instantaneous hot water heaters is permitted.

Distribution system shall consist of a piping system, which connects water heater or heaters to all plumbing fixtures as required. Circulation systems or temperature maintenance systems shall be included. Hot water shall be available at the furthest fixture from the heating source within 15 seconds of the time of operation.

Domestic Water Supply Equipment. Domestic water supply equipment shall include, but not be limited to, the following equipment:

  • Water heaters
  • Pressure booster systems
  • Pressure regulating valves Circulating pumps
  • Back flow preventers
  • Balancing valves Isolation valves
  • Hangers and supports
  • Thermal insulation

Water hammer arrestors shall be provided at every branch to multiple fixtures and on every floor for both hot and cold water.

Domestic cold and hot water distribution systems shall be insulated per ASHRAE 90.1 and all exposed piping shall have PVC jacketing.

Sanitary Waste and Vent System
Waste Pipe and Fittings. A complete sanitary collection system shall be provided for all plumbing fixtures, floor drains and kitchen equipment designed in compliance with applicable codes and standards. Piping shall be cast iron soil pipe with hub and spigot joints and fittings. Above ground piping may have no-hub joints and fittings.

Vent Piping and Fittings. System shall be the same as the waste piping above.

Floor Drains. Floor drains shall be provided in multitoilet fixture restrooms, kitchen areas, mechanical equipment rooms, locations where condensate from equipment collects, and parking garages and ramps. Single fixture toilet rooms do not require floor drains.

In general, floor drains shall be cast iron body type with 6 inch diameter nickel-bronze strainers for public toilets, kitchen areas and other public areas. Equipment room areas will require large diameter cast iron strainers and parking garages will require large diameter tractor grates. Drainage for ramps will require either trench drains or roadway inlets when exposed to rainfall. Trap primers shall be provided for all floor drains where drainage is not routinely expected from spillage, cleaning, or rainwater.

National Building Museum, Washington, DC
National Building Museum,
Washington, DC

Sanitary Waste Equipment. Specific drains in kitchen areas shall discharge into a grease interceptor before connecting into the sanitary sewer in accordance with the requirements of the state health department and local authorities will determine which drains. Floor drains and/or trench drains in garage locations are to discharge into sand/oil interceptors.

Automatic Sewage Ejectors. Sewage ejectors should only be used where gravity drainage is not possible. If they are required, only the lowest floors of the building should be connected to the sewage ejector; fixtures on upper floors should use gravity flow to the public sewer. Sewage ejectors shall be non-clog, screenless duplex pumps, with each discharge not less than 100 mm (4 inches) in diameter. They shall be connected to the emergency power system.

Rainwater Drainage System
Pipe and Fittings. Piping system shall be in compliance with local codes and sized based upon local rainfall intensity.

Roof Drains. Roof drains shall be cast iron body type with high dome grates and membrane clamping rings, manufactured by any of the major foundries. Each roof drain shall have a separate overflow drain located adjacent to it. Overflow drains will be the same drains as the roof drains except that a damming weir extension will be included.

Rainwater Drainage Equipment. Foundations drainage system with perforated drain tile collecting into a sump containing a pumping system as required by the applicable codes shall be provided.

Plumbing Fixtures
General. Provide all required plumbing fixtures including those that are indicated in the U.S. Courts Design Guides and all penal types. Fixtures shall be manufactured by companies that are approved by General Services Administration or their representatives.

All fixtures shall have sensing devices for saving water.

Natural Gas Systems
Service Entrance. Gas piping entering the building must be protected from accidental damage by vehicles, foundation settlement or vibration. Where practical, the entrance should be above grade and provided with a self tightening swing joint prior to entering the building. Gas piping shall not be placed in unventilated spaces, such as trenches or unventilated shafts, where leaking gas could accumulate and explode.

Gas Piping within Building Spaces. Gas shall not be piped through confined spaces, such as trenches or unventilated shafts. All spaces containing gas-fired equipment, such as boilers, chillers and generators, shall be mechanically ventilated. Vertical shafts carrying gas piping shall be ventilated. Gas meters shall be located in a gas meter room, thus avoiding leakage concerns and providing direct access to the local gas utility.

All gas piping inside ceiling spaces shall have plenum rated fittings.

Diaphragms and regulators in gas piping must be vented to the outside.

Fuel Oil Systems
Fuel Oil Piping. Fuel oil piping system shall use at least Schedule 40 black steel or black iron piping. Fittings shall be of the same grade as the pipe material. Valves shall be bronze, steel or iron and may be screwed, welded, flanged or grooved. Double-wall piping with a leak detection system shall be used for buried fuel piping.

Duplex fuel-oil pumps with basket strainers and exterior enclosures shall be used for pumping the oil to the fuel burning equipment.

Underground Fuel Oil Tanks. Underground fuel oil storage tanks shall be of double wall, non-metallic construction or contained in lined vaults to prevent environmental contamination. Tanks shall be sized for sufficient capacity to provide 48 hours of system operation under emergency conditions (72 hours for remote locations such as border stations). For underground tanks and piping a leak detection system, with monitors and alarms for both, is required. The installation must comply with local, State and Federal requirements, as well as EPA 40 CFR 280 and 281.

Fire Protection
Refer to Chapter 7: Fire Protection Engineering.

Last Reviewed: 2019-02-26