Water heater relief valve woes

[everyman]

I installed an old Rheem water heater that had never been used before: just sat around for fifteen years. I put in a relief valve that I had in a box of old parts. It spat out water intermittently, so I bought a new one and put that in. It also spat out water intermittently, totalling about 2 cups per day. So I bought another new one, and it does the same thing. What the ..... ?? Thanks a lot, in advance, for any help.

 

[plumbtired]

Relief valve is working. 15 year old tank prob. to blame thermostats might be stuck. Over heating making relief vale spew.

 

[phishfood]

Is there some provision made for thermal expansion? Normal expansion of the water when it is heated can cause the relief valve to discharge if there is a backflow preventor or check valve installed on the water main.

plumbtired brings up a good point as well.

 

[everyman]

Thanks very much. Is it possible to replace thermostat in a water heater?

 

[Mr_David]

Yes it can be changed.
Check the temperture of the water. Follow the instruction on the heater and make sure it's not turned up to high.
Also check you water pressure. T&p vakve can also open with excessive wtr pressure. They are usually rated at 150 PSI but can open at a low pressure.

If you were not having an expansion problem with the previous heater and leaking from T&P it's not likely that it would start doing it with this one

 

[plumbtired]

On your tank have two inspection plates . Take off you will see the thermostats . Take one wire off at a time connect to new thermostat So you know where they go . Put back on tank.

DISCONNECT POWER BEFORE DOING ANYTHING.

 

[everyman]

Thank you all.

 

[Mr_David]

Plumbtired presumed it was electric. I was thinking maybe Gas. Gas or electric?

 

[everyman]

Thank you all. Phishfood put me on the right track. I installed an expansion tank on the cold line going into the water heater, and everything, as grandpa used to say, is hunky-dory.

everyman