Fixture Water Requirements

Demand at individual water outlets

Each fixture in a water supply system represents a certain demand of water. The table below can be used to indicate the normal supply requirements of common fixtures.

FixtureFlow rateMinimum Supply Pressure
(gpm)(l/min)(psi)(kPa)
Aspirator 2.5 10 8 55
Bathtub faucet 5 19 8 55
Bidet 2 7.5 4 28
Combination fixture 4 15 8 55
Dishwashing machine 4 15 8 55
Drinking fountain jet 0.75 3 8 55
Hode bib or sillcock, 1/2" 5 19 8 55
Laundry faucet 1/2" 5 19 8 55
Laundry machine 4 15 8 55
Lavatory faucet, ordinary 2 7.5 8 55
Lavatory faucet, self closing 2.5 10 8 55
Shower head 5 19 8 55
Shower, temperature controlled 3 10 20 138
Sink faucet 3/8", 1/2" 4.5 17 8 55
Sink faucet 3/4" 6 23 8 55
Urinal flush valve 15 56 15 110
Water closet with flush valve 35 132 25 170
Water closet with gravity tank 2.5 10 8 55
Water closet with close coupled tank, ballcock 3 11 8 55

Adding up the numbers to cover all fixtures in a system would give the total demand when all fixtures are used at the same time. This is  almost never a realistic situation for a supply system. A reasonable estimate must be made based on the simultaneously demand of the fixtures.

water supply - expected demand

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