Water Heater Issue

[ExtraDuty]

I noticed that the TNP valve on my 13 year old GE Hybrid water heater was leaking (approximately a quart of water each day). I figured after 13 years, the Watts 100XL (150 psi 210 F degree) valve went bad so I went to Lowes and purchased a new Cash Acme 150 psi 210 degree F TNP Valve to replace it.

Today after morning showers, I noticed water leaking again so I started troubleshooting and here is what I found:

1. Water heater temperature is set at 115 degrees and the water temperature coming from any faucet on full hot does not seem to be above that.

2. I attached a pressure gauge to an outside hose bib, turned the water on and it went to 100psi.
I relieved the pressure from the hose bib, went inside and turned a faucet on, went back out to the hose bib and turned it on, water pressure then was 60 psi with water running in the house.
After turning the indoor faucet off, the pressure then read 80 psi and stayed at 80 psi for approximately 5 minutes before i disconnected the gauge.

Where do i go next?

~ Maybe a bad TNP valve from Lowes and replace it again?

~Has the main water pressure regulator on the incoming line gone bad? If so, How can i tell?

~Did the expansion tank go bad? If so, How can i tell?

Thanks

 

[Twowaxhack]

Expansion tank bad or pressure regulator is bad or both.

Turn your water heater to pilot and briefly open a faucet. Close all faucets, don’t use any water. Attach a gauge to a known regulated hose Bibb. Now just monitor the pressure for a little while, it shouldn’t be above 80.

If that checks good and pressure stays 80 or below, then check your thermal expansion control.

To check thermal expansion control, turn back on your water heater (tank type). Make a 5 minute draw of hot water causing your water heater to call for heat. Make sure all faucets are off and no water is being used. Attach a pressure gauge to a known regulated hose Bibb and monitor the pressure. It shouldn’t rise above 80. It should be pretty stable, it will rise a few pounds but never above 80.

Do that and report back with the results.

Your T&P valve is most likely NOT the problem.

I’m betting it’s a failed PRV ( pressure reducing valve).

 

[ExtraDuty]

After the tests, no change.

I tested the expansion tank and found that it was full of water so I replaced it first and the pressure was still high.

I bought a new pressure reducing valve and installed it. Checked the pressure and now it sits right at 45psi.

So Twowaxhack as you suggested, the "Expansion tank bad or pressure regulator is bad or both". BOTH

Thanks for the help