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Maximum possible flow rates at individual fixtures and water outlets have become generally accepted as industry practice, which have since become maximum rates set by law. Recognized flow rates at individual water outlets for various types of typical plumbing fixtures and hose connections are given in Table B.3.
For older faucets, if the applied pressure is more than twice the minimum pressure required for satisfactory water supply conditions, an excessively high discharge rate may occur. Such rates may cause the actual flow in the piping to exceed greatly the estimated probable peak demand rate determined in accordance with the standard method discussed in Section B.5. Such excessive velocity of flow and friction loss in piping may adversely affect performance and durability of the system.
More recent faucets, however, are equipped with flow limiting devices that control the discharge rate at a nearly constant value over a large range of pressures.
Where necessary, it is recommended that means to control the rate of supply should be provided in the fixture supply pipe (or otherwise) wherever the available pressure at an outlet is more than twice the minimum pressure required for satisfactory supply. For this purpose, individual regulating valves, variable orifice flow control devices, or fixed orifices may be provided. They should be designed or adjusted to control the rate of supply to be equal to or less than the maximum rates set by law.
Table B.3
MAXIMUM DEMAND AT INDIVIDUAL WATER OUTLETS
Type of Outlet Maximum Demand (gpm)
Metering lavatory faucet 0.25 gal/cycle
Public lavatory faucet 0.5 @ 60 psi
Drinking fountain jet 0.75
Private lavatory faucet 2.2 @ 60 psi
Kitchen sink faucet 2.2 @ 60 psi
Shower head 2.5 @ 80 psi
Ballcock in water closet flush tank 3.0
Dishwashing machine (domestic) 4.0
Laundry machine (8 or 16 lbs.) 4.0
Laundry sink faucet 5.0
Service sink faucet 5.0
Bath faucet, 1/2" 5.0
Hose bibb or sillcock (1/2") 5.0
1/2" flush valve (15 psi flow pressure) 15.0
1" flush valve (15 psi flow pressure) 27.0
1" flush valve (25 psi flow pressure) 35.0

Related Code Sections

210.21 Wiring and Protection, Outlet Devices
Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B ...
210.21 Wiring and Protection, Outlet Devices
Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B ...