howdy this might be a strange thing but here goes,about a year ago my water heater would make an awful noise(which I'm sure is the pop off valve)when you would flush the commode.and no the hot water is not connected to the toliet.now in the last 6 months it will do it when showering or just washing in the sink.and stops imediatelywhen the water is shut off.I have looked at the line coming from the popoff valve and there is alittle bit of water coming out of it (but only a little bit).I'm susecting my pressure reducer valve has somthing to do with it but then I can't seem to figure out why it would.have you got any thoughts on this. seeya thanks

 

Replace the Temperature & Pressure relief valve on your water heater.
Turn off the power or gas.
Turn off the cold water supply valve to the heater (or the main water valve to the house, if there isn't one).
Open a nearby hot water faucet to relieve pressure.
Wrap 2-3 flat wraps of teflon tape clockwise only around the threads of the new T&P valve as the threads face you.
Tighten it in.
Turn the water back on, and then the power or gas.
Good LucK!
Mike