[DangeloInspections]

Always glad to help.
Sometimes folks are quick to assume the T & P valve is bad, when actually it is doing it's proper job. If the Thermal Expansion tank is waterlogged the expanding water has no place to go and the relief valve will open just a bit to allow it to escape.

If a person is going to change out the expansion tank and needs to partially drain down the tank anyway, it is good practice to also replace the "leaking"
T & P valve also, as repeated opening can weaken the spring and seals inside. The cost is not much more. When doing so make sure you buy the correct rating T & P valve, as Watts makes many different types and it is easy to buy the wrong one as many will "fit" but only one will be correct. Take a picture of the tag or just bring the old one with you to make sure.......

Frank D'Angelo