Re: New Expansion Tank/T&P Valve Still Leaking
If this hasn't been mentioned by now....it should be pretty easy to determine if the PRV is at fault here.
Open a faucet and run some water to stabilize the pressure at 40 psi. Might just as well do this at a hot water faucet and draw enough water that the WH is sure to kick in. Then close the valve on the main house supply so that no more water can enter the system anywhere (WH or the cold water lines). Hopefully you have such a valve upstream of your new expansion tank AND it closes dead tight cause any introduction of water into the system will skew this test...rendering it worthless. Likely you have one just upstream of the PRV which allows you to service that if/when it needs it. Then wait and see what happens.
If the T&P doesn't drip/pressure doesn't build to excess...this should be confirmation that 1- you don't have a runaway heating element and 2- that the expansion tank is doing the job it's designed for.
If all is well at the end of that little test...open the main supply valve again and see if the pressure builds. If it does...you gotta faulty PRV. I suspect that this what you will discover....but I've been wrong before. Just once to the best of my memory. <G>
Last edited by goldhiller; 09-17-2008 at 09:48 PM.