Water Main Shut off and Electric Hot Water Heater

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mrmichaeljmoore, Jan 6, 2010.

  1. mrmichaeljmoore

    mrmichaeljmoore Member

    Jan 17, 2007
    I have a question regarding turning off the main water supply to the house but leaving the hot water heater on. The water heater is a Whirpool ELECTRIC water heater. I think it is 40 gallon.
    Here's the backstory: I came home last night to find that the supply line to my basment utility sink had worked its way loose, dumping a few inches of water onto my basement floor.

    Needless to say, I am now a bit paranoid about leaving the house and coming home to find a pool in my basement.

    So, I was thinking that when I leave for work in the morning, or go away for the weekend I will turn off the well pump switch and close the ball valve at the bottom of the well retention tank....thereby if I do get a leak, only what is in the lines will come out...

    But, I remember reading somewhere that turning off the water supply, but leaving the hot water heater on could cause a problem. Something about evaporation in the water heater tank??

    So, here are my questions:

    1. If I decide that everytime I leave the house, I will turn off the main water supply to the house, should I turn off the breaker to the water heater?
    2. How long can the tank sit powered on, but with the water supply closed?
    3. Would I need to turn it off daily when I leave for work or only when I go away for a few days?


  2. nukeman

    nukeman Nuclear Engineer

    Nov 20, 2009
    Nuclear Engineer
    I shut mine off if I am going to be gone a couple days. I had the T&P open on the water heater (we were home, but outside) and it flooded things pretty good. If we were away, it would have been much worse.

    Kill the breaker to the WH too when the water is off. If the water level were to drop below the heater element when the power was on, the element would burn out quickly.

    It really only makes sense to turn off water when away for an extended period. If you are worried on a day-to-day basis, there are water detection sensors that can work as an alarm or to control a valve to cut off water if water is detected on the floor.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    You could just turn the pump off. The storage tank (if the check valve works), should keep the house pressurized, but limit the amount of water that could leak out. You don't want to chance running the WH low, as noted, it will burn out the element almost instantly.
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