Question
Two of my irrigation valve "squeal" when they are activated.  Any ideas of what causes this?  I change the diaphragm on one valve, but that did not help.

Answer
There could be a couple of reasons.  One is that the valve needs to have the flow adjusted.  Do this by opening the flow control on top of the valve all the way, then close it all the way, counting the turns, then open it back halfway.  The other reason could be that there is too much water pressure on the upstream side of the valve.  To correct this you would need to install a pressure regulator in the main line supplying the valves.