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.

Fixture Flow rate Minimum 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
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 3/8″, 1/2″ 4,5 17 8 55
Sink 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.