I got new sprinkler valves put in (Rainbird anti-siphon kind). Every time a valve shuts off, it makes a loud squeak, kind of like plastic rubbing (NOT a bang like water hammering). Is this normal and will it go away? If not, what could be the problem? This is annoying because the sound can be heard in the house as it echoes through the pipes.
Rainbird Anti Siphon Valve
As the valve shuts down, the diaphragm will vibrate as the pressure changes from one side to the other, then it will Thump as it seals. This is normal. However, to isolate the squeak, you may check to see if there is a 1(backflow preventer installed, 2) (if built into the valves) the variable pressure screw on the top of the valve is set correctly. The variable pressure screw usually has a cross top handle (older ones had a dial) and should be set so that on a high pressure line, it shuts down fairly quickly. If this is open all of the way, it can cause the diaphragm to squeal by slowing the internal pressure change to shut it down.