Water Heater Noise

[DrivesBGM]

While camping this past weekend the water heater started to sound like water was running through it. All water was turned off. The heater was being run on AC. I checked and the hot water had normal temperature and pressure.

I tripped the AC breaker for the water heater and the noise stopped within a few seconds. I reset the breaker and the noise started almost immediately.

I then turned the breaker off and went to bed. I turned it back on in the morning and have not heard any noise out for it for two days.

Any ideas as to what problem might be developing?

Thanks,
Craig