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ehits

Question on Velocity, GPM, and Water Hammer

ehits
9 years ago

Hello, I used irrigationtutorials.com to help me design my lawn's irrigation system. My available GPM is a safe 11gpm at 60psi. I also have a total pressure loss of about 58psi. I have 3 zones with 2 of them flowing 7.4 GPM each and one flowing 1.56 GPM. My SCH40 PVC supply pipe is 1". After the valves, it goes 1" part way and 3/4" to the ends. Most calculations err on the conservative side for safety.

So I should run each zone on its own valve, but it would be convenient to run the 2 bigger zones together. For fun I manually ran all three zones at once and was surprised to see that I still get full coverage. I tried again with just the 2 big zones together and again it ran fine. Turning off the valves simultaneously gave me no audible water hammer.

Is it safe to run these 2 zones together? According to my calculations, this exceeds my design capabilities (in terms of GPM and velocity), but in reality it appears to run fine. Is there unseen damage I may cause? Any wisdom about irrigation that I am not seeing or understanding? I am no pro, but feel I confident in my calculations. Thanks for any input!

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