I own a 2 year old 2 family house. I have 2 AO Smith 50 gallon (high efficiency water heaters). They are 2 years old. Last week I noticed that the T&P valve on one of the units developed a very slow drip. Literally 1 drop every few minutes (very minimal). I opened and closed the valve for a few seconds and now the drip has slightly increased -- approx 1 drop every 20 seconds. (1/2 of a coffee can in 5 days)

I doubt that it is a pressure problem with my city water supply. If so, would not both water heaters experience the same problem as they are both tied into the same city water supply? Can it be a bad valve after only 2 years? Should I continue to open and close it to see if it will seat more appropriately?

Please help

Hi Mike...

Sometimes a temperature and pressure relief valve can simply go bad. I say you replace the defective T&P valve and see how things go. I'm betting you'll be all set.

If you want to be absolutely sure that all is good you can always take a temperature reading of the hot water using a cooking thermometer made for just this pupose... sold at home depot... see image. A hot water heater, especially in a multi. Family dwelling, should not exceed 120F. If you exceed that temp. lower it down to 120F for safety. If you exceed that temperature in a range like 140-150F then that could definitely increase the pressure and lead to premature failure of a T&P valve. If the temperature exceeds 150F shut that water heater off and pop back to us for more info.

You can also check for pressure using a pressure gauge... also sold at home depot, but I don't think it is necessary at this time.

Replace the T&P valve for now... don't forget some teflon tape when you purchase the new valve... ;)

MARK

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3 things cause water to come out of a T&P; water temps over 210, pressure higher than 150 psi and junk on the seal of the T&P. Like Mass points out, they can just go bad and only get worse as you have found out. Your home works best with 45 psi and 120 degree hot water so test for those ranges like Mark suggests.