P2903.8 Gridded and Parallel Water Distribution Systems

PLASTIC		METALLIC
Nominal Size ID (inches)	Maximumb gpm	Nominal Size ID (inches)	Maximumb gpm
3/4	17	3/4	11
1	29	1	20
11/4	46	11/4	31
11/2	66	11/2	44

For SI: 1 inch = 25.4 mm, 1 gallon per minute = 3.785 L/m, 1 foot per second = 0.3048 m/s.

1. See Table P2903.6 for w.s.f.u and Table P2903.6(1) for gallon-per-minute (gpm) flow rates.
2. Based on velocity limitation: plastic, 12 feet per second; metal, 8 feet per second.

Where the developed length of the distribution line is 60 feet (18 288 mm) or less, and the available pressure at the meter is not less than 40 pounds per square inch (276 kPa), the size of individual distribution lines shall be not less than ³/₈ inch (10 mm) diameter. Certain fixtures such as one-piece water closets and whirlpool bathtubs shall require a larger size where specified by the manufacturer. Where a water heater is fed from the end of a cold water manifold, the manifold shall be one size larger than the water heater feed.

Plastic piping bundles shall be secured in accordance with the manufacturer's instructions and supported in accordance with Section P2605. Bundles that have a change in direction equal to or greater than 45 degrees (0.79 rad) shall be protected from chafing at the point of contact with framing members by sleeving or wrapping.

Fixture valves, when installed, shall be located either at the fixture or at the manifold. Valves installed at the manifold shall be labeled indicating the fixture served.

A readily accessible air bleed shall be installed in hose bibb supplies at the manifold or at the hose bibb exit point.