Welcome! Here are the website rules, as well as some tips for using this forum.

# Water piping flow rates

Member Posts: 2
The wide open rule of the thumb is no water hammer and laminar flow. for most piping that is limited at 5 feet per second water flow rate. Calculate the volume of water in a foot of the pipe you want to use. convert it to gallons, Now use that and 5 feet times 6o seconds for one minute then times 60 for the hour. answer is in gph. 3/4 Cu pipe is close at 4 gpm (240 gph)

• Member Posts: 86
Flow rates

Anybody know where I can get a formula for the flow rate of copper tubing at diferent preasures in GPM.
I think I should know this.

Rich Swatton
• Member Posts: 6,106
The PHCC

had this nice calculator wheel for this puropse. It was based on the National Bureau of Standards 66 & 79. I'll bet this is available online somewhere, now a days. It gave various GPM at both 4 FPS and 8 FPS velocities.

3/4 copper flowing 11.6 GPM, 7.7 FPS with a whooping 18 psi loss per 100 feet of pipe

At 3.3 FPS, 5 GPM with 3.9 psi pressure loss per 100 feet of pipe.

hot rod