Is the water hammer on EVERY valve? Run thru' the system and ID which valve causes the problem. If it's all the valves, then Tom and WetBoots have nailed it. You have to slow the water down, and in some cases, using head that have considerabley less flow in gpm, can solve the problem. I've also managed to get hamering to stop by adding a hydro arrestor at the far end of the mainline (IF it isn't branched.) This isn't really a proper fix, but it has stopped the banging for some customers.
The Irrigation Specialist Mfg' Az.
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Real timesavers, especially the Suck-Tube and Krik-It.
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