What is the maximum flow rate of non-freeze wall hydrants?

Generally speaking, the average GPM (gallons per minute) you can expect from an outside non-freeze wall faucet with a ¾” inlet connection and a ¾” garden hose bibb outlet (in the fully opened position), is between 5-9 GPM with a system water pressure of 50-60 PSI. This pressure is typical for municipal water systems but is on the high end for most domestic well systems which are commonly operated between 30-50 or 40-60 PSI.

VELOCITY:

Ideally, the flow velocity should be around 5 FPS (feet per second), with 7 FPS being the upper limit.

It is also important to take flow velocity into consideration when selecting a valve. A larger pipe is more expensive; however, this can be useful to keep the flow velocity low. A low flow velocity helps to limit pressure losses due to friction, water hammer, and pipe movement due to water momentum changes inside the pipe. It is recommended to size piping to maintain a flow velocity of 5 FPS (1.524 LPM). 5 FPS is a threshold that is widely accepted by engineers and designers because beyond this velocity, the friction losses, danger of water hammer, and pipe movement due to water momentum changes are deemed to be too high.

FRICTION LOSS:

When 50 to 100 feet of 5/8” garden hose is added to the system, the flow rate drops to around 5-6 GPM. The flow rates could be even lower if the hose bibb was plumbed in 1/2” supply pipe instead of 3/4” pipe. Flow rates could drop even further if the length of the supply line from the sources is long and includes any number of elbows fitting before getting to the hose bibb. These factors will increase the friction loss and further reduce the GPM at the destination.

SOLUTION FOR 10 PLUS GPM REQUIREMENT:

Boshart does not carry commercial wall hydrants that will provide flow rates in the 10 to 20 GPM range. A “commercial” non-freeze wall hydrant with a 1” inlet connection would be required to get a 15-20 GPM flow rate.

Additional Resources:

For more information regarding non-freeze wall hydrants and replacement parts, refer to the articles linked below.

https://support.boshart.com/can-i-leave-my-non-freeze-wall-hydrant-under-continuous-water-pressure

https://support.boshart.com/how-to-install-a-m08qtwh-quarter-turn-frost-proof-wall-hydrant

https://support.boshart.com/are-replacement-parts-available-for-the-0865-series-wall-hydrants