SECTION P-604 DESIGN OF BUILDING WATER DISTRIBUTION SUPPLY SYSTEM

P-604.1 General. The design of the water distribution supply system shall conform to accepted engineering practice. Methods utilized to determine pipe sizes shall be approved.

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P-604.3 Water distribution supply system design criteria. The water distribution supply 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 be not less than shown in Table P-604.3. The minimum flow rate and flow pressure provided to fixtures and appliances not listed in Table P-604.3 shall be in accordance with the manufacturer's installation instructions.

TABLE P-604.3
WATER DISTRIBUTION SUPPLY SYSTEM DESIGN CRITERIA REQUIRED CAPACITY AT FIXTURE SUPPLY PIPE OUTLETS

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P-604.5 Size of fixture supply. The minimum size of a fixture supply pipe shall be as shown in Table 604.5. The fixture supply pipe shall terminate not more than 30 inches (762 mm) from the point of connection to the fixture. A reduced size flexible water connector installed between the supply pipe and the fixture shall be of an approved type. The supply pipe shall extend to the floor or wall adjacent to the fixture. The minimum size of individual distribution supply lines utilized in gridded or parallel water distribution systems shall be as shown in Table 604.5. A ridged water connector shall be required in all occupancies other than one- and two-family dwellings.  367

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P-604.6 Variable street pressures. Where street water main pressures fluctuate, the building water distribution supply system shall be designed for the minimum pressure available.

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P-604.8 Water pressure-reducing valve or regulator. Where water pressure within a building exceeds 80 psi (552 kPa) static, an approved water pressure-reducing valve conforming to ASSE 1003 or CSA B356 with strainer shall be installed to reduce the pressure in the building water distribution supply piping to not greater than 80 psi (552 kPa) static.

Exception: Service lines to sill cocks and outside hydrants, and main supply risers where pressure from the mains is reduced to 80 psi (552 kPa) or less at individual fixtures.

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P-604.9 Water hammer. The flow velocity of the water distribution supply system shall be controlled to reduce the possibility of water hammer. A water-hammer arrestor shall be installed where quick-closing valves are utilized. Water-hammer arrestors shall be installed in accordance with the manufacturer's instructions. Water-hammer arrestors shall conform to ASSE 1010.

P-604.10 Gridded and parallel water distribution supply system manifolds. Hot water and cold water manifolds installed with gridded or parallel connected individual distribution supply lines to each fixture or fixture fitting shall be designed in accordance with Sections 604.10.1 through 604.10.3.

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Notes

367	Amended, Bill No. 230653 (approved December 20, 2023), effective April 1, 2024.