My sprinkler system has started to make a horn like sound when it turns on. Every thing is working, spay is fine etc.

Any suggestions?

The sound is inside the house?

I can hear it inside. When I activate the valves at the boxes it’s not so loud.

I haven’t checked the ones by the back flow preventer to see if I could hear it but it sounds like it’s coming from the other side of the house.

There's a pressure reduction valve in some applications at the water shut off in your house. When that valve goes bad it makes noise like you are describing

quote:

Originally posted by darthfuster:
There's a pressure reduction valve in some applications at the water shut off in your house. When that valve goes bad it makes noise like you are describing

Yep. If you're brave you can be part of the 0.01% which rebuild such devices. The other safety component, a backflow device, will make a noise like an automatic sprinkler while gushing water. ... I installed a Sloan urinal Flushometer with a diaphragm closure device (different application but somewhat similar in its engineering) make a frog-like noise every time it shut off. Couldn't adjust the noise away and eventually left it alone.