I travel quite a bit and so leave my water heater breaker off - as I travel for extended periods (months). In the past I used to leave the main water valve (near the meter) on - and would turn off individual shut off valves to the toilets, under the sinks etc...

during my last travel someone looking after the property decided to turn off the main and left the circuit breaker on. A few days later I had damage to the ceiling and laminate flooring. so I guesses with cold water off the pressure may have built up and that's why it leaked (circuit was on).

So I experimented again and earlier today (Oct 17 2014) I turned off the water and the circuit breaker and within an hour water was overflowing from the catch pan - so it looks like the drain connection from the pan is also clogged.

But more importantly why does the tank leak only when the main is off - i have been in the condo for two weeks now and the pan has been dry.

What causes the tank to leak under these circumstances? Do I need to replace it? Mfg date is: 01/2006 installed in FL state. 50 Gal rheem.

any advice feedback would be appreciated.

  • it could have overheated when the main was off and breaker was on Oct 17, 2014 at 23:34
  • Does this happen when only the main is off, or when both the main and circuit breaker are off?
    – Tester101
    Oct 18, 2014 at 5:30

1 Answer 1


By shutting off the water main, there is no way for expanded hot water to be relieved by backing into the main. This causes over-pressure and either the pressure relief valve is letting some water out (hopefully into the pan) or the high pressure water is opening a flaw in the tank or a through-hole, such as a heating element, spigot, or water connection.

The water temperature is not held perfectly steady. It varies up and down by perhaps 20 °F (10 °C) or more. (Test this by turning the thermostat up and down and notice how far it goes past the current temperature before it clicks.) If no hot water has been called for awhile, the temperature drifts down to the lower range and remains there most of the time. Odds are that closing the main valve occurs at a lower water temperature. The valve closure traps and holds municipal water pressure and then the water heater's next heating cycle builds pressure on top of that.

  • Thanks for responses. Ok so after my initial post - I continued with my experiments/diagnosis. When main is off and all other taps in the house are off (not the shutoff values) there is no leaks. As soon as I opened one of the taps - water started leaking from the shutoff vale on the tank. the valve was open position. When the shutoff value is closed no more leaks. When The water main is on and the valve is on -no leaks. I'm going to bite the bullet and just change the tank - can't risk another cycle of damage. I've decided to relocate the tank to the garage. Any suggestions?
    – MMJ
    Oct 21, 2014 at 18:29

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