New Expansion Tank noise after somebody takes a shower or lots of hot water use...

I installed a new gas water heater(GE 40 gallon), and Watts(DET-5 2.1Gallon) expansion tank a few weeks ago. All is working fine, except I noticed that when somebody takes a shower or somebody turns on the hot water full bore like doing dishes in the sink, there is a little bit of noise coming from the expansion tank. It only lasts for a few minutes, kind of a groaning noise, like something hot inside cooling down maybe or maybe air settling? It has done this since the first day of install, I am just slow in getting around to asking about this. And you wouldn't hear it unless you are in the same room as the water heater. Maybe it is normal to hear a little noise from it after a lot of hot water get's used, I don't know. Thanks.

Expansion tanks generally do not make noises. Now, if the tank is not well supported, as the water level in it changes (the weight changes), it may be the pipes leading to it that are moving, and you hear that. The pipe (if the tank hangs down) need to be supported around the T to the tank. Or, the tank itself needs to be supported if it is horizontal.

The air pressure in the tank may be low and needs checking. These cheap beer cans often dont last long.

Okay I can check the pressure which I set to about 45psi, which was same as pressure in house. I turn off water supply, open a faucet to let the pressure out then stick an air pressure gauge on the expansion tank to check it?

DoofusOfTheDay said:

Okay I can check the pressure which I set to about 45psi, which was same as pressure in house. I turn off water supply, open a faucet to let the pressure out then stick an air pressure gauge on the expansion tank to check it?

Click to expand...

Yes, all water pressure must be off to check the air pressure in the tank otherwise, the reading will be of the water pressure (if the water pressure is higher than the air pressure to start with). It is also a convenient place to check your water pressure as most people do have a tire pressure gauge, but may not own a water pressure gauge.