Dual Check Valves high pitch sound

[nganchris]

Hi,
I recently installed a Watts dual check valves on the lawn sprinkler line. The supply side Tee off a pressure regulator which is set to 60 PSI.
The problem is I can hear a high pitch whining noise when no water is running (either to the sprinkler heads or inside the house).

I am not detecting leaks either by watching the water meter.

This happens mostly during the day when the sun is shinning on the valve.

Anyone has any idea? Could it be a defective valve?

 

[johnjh2o]

I would say it's the regulator that's causing the whining not the check. The regulator may be leaking by. Check the pressure on the outlet side of the regulator and see if it creeps up.