sudden water spikes/surges

[olderguy]

House is on crawlspace, just before the water main goes under the foundation, it tees of to feed the irrigation system, 9 sprinkler valves. The water is 75psi at an outside hose bibb which of course is after it come under house and supplies house plumbing. last fall I began having several leaks and problem with 2003 installed cpvc. I had a repipe done with worsbo PEX. Now I am hearing water hammer noises when the sprinkler valves close. When sprinklers are on pressure drops to about 40 at the hose bibb, and when sprinkler valve closes, spikes to about 110psi. I checked with a tell tale guage. I had a water hammer aresster installed but it did no good, still get water surge/spike. My question is , Would a pressure reducing valve set at 75psi stop the sudden surge from spiking from 40 to 110, or would that much water pressure surge just go through the PRV and still get the sudden surge??

 

[Mr_David]

I have seen solenoid valves slam shut and cause a spike. You say spike. do you mean that you have a gauge and when the sprinkler shuts off the needle jumps to 110 for a moment like a bounce and then settles to a lower pressure. or does the pressure remain at 110?

Do you have a prv now. what is the pressure before the sprinkler come on?

Could be the exiting PRV is not working properly or the spike is caused by the solenoid is slamming shut.

 

[olderguy]

actualy The pressure remains at 110 until a faucet is opened or I loosen the guage, I never left it on for an extended period of time to see if the guage settled back down. pressure before sprinkler comes on is 75psi and then with sprinklers running drops to around 40psi in the house. don't have a prv now and I do have an expansion tank on water heater , also the city has a backflow preventer at the meter at the curb, so no water can expand back that way either.

 

[Mr_David]

Put a Regulator on the line to house after the sprinkler
Drop the pressure down to 50-60 psi.

 

[olderguy]

That is what I am considering doing , I just wanted to know before I do if the regulator will stop the water surge/spike. I am also considering changing out the sprinkler valves to a slow closing valve.