HW heater tank loses pressure

[vakil01]

My daughter's hw heater is noisy and I noticed it filling about once every two hours even though no one is using any water. The fill period is short - maybe 30 seconds. The tank is not leaking and I have asked her to look for a low hw leak somewhere.

My question is whether there could also be a problem with the pressure relief system.

Thanks,

 

[johnjh2o]

Water heaters are full at all times unless you turn the water off and drain it. If the relief valve is dumping there would be water coming out of the line connected to the relief valve.

 

[klee181438]

Do you mean heating up or filling? If it were filling, you would have air coming through your fixtures until full. As johnjh20 says, a water heater stays full at all times

 

[vakil01]

The sound is filling - water running through pipe.

 

[Caduceus]

Kinda sounds like you have a toilet that is losing water and the tank of the toilet is refilling. The sound may be heard anywhere in the water piping system, even tricking you into thinking it's from the water heater.
Especially if the cold water branches off close to the water heater supplies.
If you can, shut off the valves to the toilet(s) supplies for about two hours without using the toilet(s). Then after a while have your daughter open the valve(s) one at a time while you are by the water heater.
If it's a toilet actually refilling due to a leaky flapper or flush valve, she should hear it filling at the toilet and you may also recognize the sound at the heater as the sound you heard before.
It worth a try to eliminate the possibility.