The Chicago Plumbing Code

§ 18-29-604

§ 18-29-604.1 General.

The design of the water distribution system shall conform to accepted engineering practice. Methods utilized to determine pipe sizes shall be approved by the commissioner of water.

§ 18-29-604.2 System interconnection.

At the points of interconnection between the hot and cold water supply piping systems and the individual fixtures, appliances or devices, provisions shall be made to prevent flow between such piping systems.

§ 18-29-604.3 Water distribution system design criteria.

The water distribution system shall be designed, and pipe sizes shall be selected such that under conditions of peak demand, the capacities at the fixture supply pipe outlets shall not be less than shown in Table § 18-29-604.3.

§ 18-29-604.4 Maximum flow and water consumption.

The maximum water consumption flow rates and quantities for all plumbing fixtures and fixture fittings shall be in accordance with Table § 18-29-604.4. Water consumption for urinals listed in the following exceptions shall not be greater than 1.5 gallons (5.7 L) per flushing cycle.


  1. Blowout design fixtures.
  2. Penalware.
  3. Clinical sinks.
  4. Service sinks.
  5. Emergency showers.

§ 18-29-604.4.1 Deliberately omitted.*

*Note - Coun. J. 3-28-01, p. 55444, 1, did not provide for a Section § 18-29-604.4.1.

§ 18-29-604.4.2 Water closets.

Water consumption for water closets listed in the following exceptions shall not be greater than 4 gallons (15 L) per flushing cycle.


  1. Water closets provided for the public in theaters, nightclubs, restaurant, halls, museums, coliseums, arenas, churches, schools, stadiums and similar occupancies.
  2. Water closets provided for patients and residents in, hospitals, nursing homes, sanitariums and similar occupancies.
  3. Water closets provided for inmates and residents in prisons, asylums, reformatories and similar occupancies.

§ 18-29-604.5 Size of fixture supply.

The minimum size of a fixture supply pipe shall be as shown in Table § 18-29-604.5. The fixture supply pipe shall not terminate more than 30 inches (762 mm) from the point of connection to the fixture. A reduced-size connector installed between the supply pipe and the fixture shall be of approved type. The supply pipe shall extend to the floor or wall adjacent to the fixture.

§ 18-29-604.5.1 Minimum size.

The minimum size of individual distribution lines utilized in parallel water distribution systems shall be as shown in Table § 18-29-604.5.

§ 18-29-604.6 Variable street pressures.

Where street water main pressures fluctuate, the building water distribution system shall be designed for the minimum pressure available.

§ 18-29-604.7 Inadequate water pressure.

Wherever water pressure from the street main or other source of supply is insufficient to provide flow pressures at fixture outlets as required under Section § 18-29-604.3, a water pressure booster system conforming to Section § 18-29-606.5 shall be installed on the building water supply system.

§ 18-29-604.8 Water pressure reducing valve or regulator.

Where water pressure within a building exceeds 100 psi (690 kPa) static at any fixture or outlet, an approved water pressure reducing valve conforming to ASSE 1003 with strainer shall be installed to reduce the pressure at any fixture or outlet in the building water distribution piping to 100 psi (690 kPa) static or less.

§ 18-29-604.8.1 Valve design.

The pressure reducing valve shall be designed to remain closed in case of valve failure.

§ 18-29-604.8.2 Repair and removal.

All water pressure reducing valves, regulators and strainers shall be so constructed and installed as to permit repair or removal of parts without breaking a pipeline or removing the valve and strainer from the pipeline.

§ 18-29-604.9 Deliberately omitted.

§ 18-29-604.10 Size of water supply pipes.

Each main supply pipe, principal supply pipe, branch supply pipe, riser pipe, distributing pipe, or branch distributing pipe shall be of a size which under normal pressure shall deliver a full volume of water to each and all of its outlets.

§ 18-29-604.10.1 Minimum sizes of branch distributing pipes for fixtures and appliances.

The water supply system shall be designed on the basis of the minimum available pressure at the water main or other source of water supply. The minimum available pressure will be given by the department of water for each location.

§ 18-29-604.10.1.1 Demand load.

The water supply demand load in the distributing system shall be based upon the number, type, and probable simultaneous use of the fixtures to be supplied.

§ 18-29-604.10.1.2 Size of piping.

The size of piping shall be such that the velocity of each flow during maximum demand will not exceed 8 feet (2440 mm) per second velocity in the main supply pipe, principal supply pipe, and branch supply pipe. When a water service requires a pump, the velocity of flow in the service shall not exceed 5 feet (1525 mm) per second velocity.

§ 18-29-604.10.1.3 Available pressure.

In determining the available pressure to overcome friction in the piping system, head meter and other losses shall be deducted from the minimum available pressure source. When the pressure exceeds 100 psi (690 kPa) at any plumbing fixture, the pressure shall be reduced by an approved type reducing valve. The minimum size of fixture supply pipes are shown in Table § 18-29-604.5.

§ 18-29-604.10.2 Procedures for calculating sizing.

See Appendix A for procedures for sizing of the water supply system.

§ 18-29-604.11 Air chambers required.

Air chambers shall be installed at the upper terminals of all upfeed riser pipes and in branch distributing pipes contiguous to, and directly above, the connection of such branch distributing pipes to the plumbing fixture or other water-supplied appliance. Such air chambers shall be installed in a direct line with the flow of water through such pipes and shall be of sufficient capacity to provide an air cushion which will absorb shock, stress, or strain or eliminate all excess noises which may be caused by the operation of any valves, faucets, bibbs, or cocks in the water supply system.

§ 18-29-604.11.1 Size of air chamber.

No air chamber which is constructed of pipe shall be of a size less than the pipe which it serves and to which it is connected and shall be not less than 2 feet (610 mm) in length. The air chamber on each water supply branch connection to a plumbing fixture shall be not less than 12 inches (300 mm) long.