Temperature Pressure Relief Valve

tjw61 · Jul 20, 2008

Hi,

The Temperature Pressure Relief Valve on my 9 year old AO Smith water heater has started to drip. It only does this when we use our central air. Any ideas on why or what I should do about it? I am planning on replacing the valve tomorrow, but find it curious that it only leaks when the air is in. The water heater is about 4 feet from the furnace, which is what circulates the air. It's a forced hot air system. Any help will be appreciated.

Thanks,

tj

T&P Valve looking at two sides.

Mike Swearingen · Jul 20, 2008

Just replace the T&P valve. That will do it.
I have no idea why it only leaks when the AC is on. One should have nothing to do with the other.
Mike

Sponsor · 2022-01-29T12:20:58-0800

tjw61 · Jul 20, 2008

Thanks.....that's what I thought, but I figured I'd ask!

B2CHR · Jul 20, 2008

Now just a guess here but maybe with the air on and the house colder it is cooling down the water lines and causing the water heater to come on more. Just a guess.

tjw61 · Jul 20, 2008

That makes sense.......

Redwood · Jul 20, 2008

Lets get a pressure measurement and make sure that it is not just doing its job!

tjw61 · Jul 23, 2008

Thanks, it turns out it was the water heater expansion tank. It had blown and wasn't regulating the pressure correctly. The pressure in the tank was @ 110 PSI. After replacing it, it turned out the Temperature Pressure Relief Valve wouldn't reseat and it was replaced also. Turns out the AC thing was just bad timing!

Thanks again,

tj

Jadnashua · Jul 23, 2008

An expansion tank is sort of like a balloon inside of a tank. You blow the bladder up to the normal water pressure, then as the water expands during a heating cycle, it collapses the balloon some in the tank. It won't regulate water pressure.

bebenterprises · Jul 24, 2008

I would say that you either don't have a pressure regulator or you have a bad one. The expansion tank is not intended to regulate the water pressure down. If you look at the installation instructions on the expansion tank for a domestic hot water system, they usually say to set it to the same pressure as the home's water pressure. A new Temperature and Pressure Relief Valve (TNP) will also leak. Some pop off at 150 psi, others at 125 psi. Either way, if your cold water is coming in at 110 psi, the TNP will release once the water is heated.

Temperature Pressure Relief Valve

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