Water hammer

I recently replaced the solenoids on my two Lawn Genie automatic anti-siphon lawn sprinkler valves and now there is water hammer when they shut off. They come on go off individually, back to back. I've had the valves for several years and this is the time I've replaced the solenoids. Is there a fix for the water hammer?
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anti-siphon
a
The 'hammer' comes from all the water in the pipe run leading to your valves being stopped all the sudden. This can happen with sinks and elsewhere inside the home.
The usual fix is to run a pipe straight up and cap it, close to the valve. Air will be trapped in there, acting like a shock absorber for the water.
Pagan
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If you can add a tank or piece of pipe vertically, in front of the valves, you can reduce the effects of water hammer. High water pressure is the culprit. I work with ice machines that have this same problem. The mfg. changes vendors on valves and all of the sudden you have these noises. The idea behind the tank or length of vertical pipe, is that all water pipes have a little air in them. If you can trap a little of this air, you can create a shock absorber (so to speak) th reduce but probalbly not stop the hammering. This will also let the valves last longer and is most likely what caused the old valves to fail. When I built my house, I installed a 1' length of 1" copper pipe w/ a cap, on each cold and hot faucet supply line. I tee'd them into the supply line inside the wall and added a enough standard pipe to make sure they 1" pipe would be higher than any fixture they were serving. PVC pipe would work for your application. Follow pressure glueing info. Good luck Lyndell
P.S. If there is a lot of construction in your area, the water company has been forced to increase pressure to keep up with demand. I forgot to mention that a water pressure regulating valve (inlet side of the valves) would also do the trick.

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