I have a 3.5 year old 40 gallon 12 year Whirlpool water heater with the diagnostic box on top. For 3.5 years (installed new) we have had no problem with this tank but now the T&P valve is leaking. About a month ago we stated seeing a very small amount of water in the drain pan below the water heater. After inspecting we found it was coming from the T&P. I replaced the T&P but it didn't fix the problem. I called a plumber who replaced my pressure regulator at the road (adjacent to the city water supply/water meter). This didn't fix it either. Talked to a couple more plumbers and they said it was just bad luck and it was another bad T&P. Changed it again - still didn't fix the problem. Original plumber says we need to install a thermal expansion tank. Why would I have not had any problem for 3.5 years and now I need an expansion tank??? What could have changed with my system to make us need an expansion tank now??? Is there anything else that could be wrong with the water heater that could be causing the T&P to leak. It is just a small amount of water each day - maybe 1/2 a cup or so??? Can anyone explain? Please help! Thanks, Toby

 

what has changed is that the heater is getting older and thus is not as efficient as it was when new. you have a pressure problem and an expansion tank is about the only cure.

the t&p valve s a temperature and pressure valve. with just a little dribbling fom the valve it suggest a problem with the pressure in your system whcih is common to a closed system such as yours, if it was a temperature problem the water would be gushing out until the water in the tank was cool enough for the valve to close.