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Active Member


Tuesday, January 3rd 2006, 8:05pm

Water hammer?

I'm just starting to design my first sprinkler system... I went over to a friends house the other day and he showed me a system he just installed a couple of months ago. He turned on and off some of the valves for me to show me his controller and I noticed a rumbling sound when the valves shut off. I didn't say anything, but I think that it was major water hammer. I looked at a couple sites and they said to avoid water hammer, the flow rate of the water through the pipes should be less than 7ft/sec.

Is this a good number to use[?]
Is there a website where the I.D. of all the pipes are specified? (Cu, PVC, etc)[?]



Advanced Member


Wednesday, January 4th 2006, 2:33am

Check out this web site

Lot's of useful information


Supreme Member

Posts: 314

Location: USA


Wednesday, January 4th 2006, 11:40am

The above listed site is an excellent reference. It will give you the different appropriate flow rates for different sizes of piping. It will also explain water hammer, and how to avoid it.
Tony Posey
Ridge Run Landscapes


Supreme Member


Tuesday, January 10th 2006, 11:38am

I would aim for 5 feet per second.

Use high quailty valves, not the cheap 10 to 20 dollar valves. For example, Rainbird PGA series valves cost more but they they close slowly in comparison to their popular DV series valves.


New Member

Posts: 4

Location: USA


Tuesday, February 21st 2006, 1:31pm

also avoid 90 deg. elbows when possible this constricts flow and adds to the knock in pipe systems


Advanced Member


Sunday, March 19th 2006, 6:47pm

you can install an expansion tank. it looks like a small propane tank but it is used in plumbing. easy to install it threads on to any slip by slip by thread copper fitting. install after the sprinkler shutoff. also using the correct electric valves help a lot!!!! some valves open and close very fast and in high pressure areas will cause water hammer. other valves close slow and may help eliminate or soften the hammer. hunter valves are great for this. hope this helps.

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