How to properly shut off one hot water tank in a parallel system?

Discussion in 'Water Heater Forum, Tanks' started by joeyw, Sep 8, 2011.

  1. joeyw

    joeyw New Member

    Sep 8, 2011
    Hi, I have two gas hot water heaters that are setup in parallel and I only need one. I'm just not sure of the proper "step by step" procedure to turn off one of them ?

    Thanks alot,
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Jan 5, 2008
    Test, Don't Guess!
    Land of Cheese
    The heaters would likely both last longer if you set the first one to heat to a medium temperature and then the second to your normal "hot" water temp.

    If you shut one down and drain it, it will be likely to corrode quite rapidly. If you leave water in it, it could harbor bacteria.

    If you really want to shut it down, it should be removed from the plumbing system.
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  4. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Nov 20, 2008
    Chicago Illinois Licensed Plumber
    Chicago, IL

    That only works if the heaters are in series, in Parallel they need to be set to same temperatures. If you have them set to different temps in a parallel the cooler heater will temper the water from the higher temp heater.

    Now to answer the OP question, you would turn off the water shut off to the heater you want to turn off and turn off the gas to the same heater. Casher_Chick does have one thing right and that is you would be violating the code by creating a dead end fixture and piping. It’s best to remove it completely and remove the piping that would run to the heater that you removed to eliminate any dead ends in the plumbing system.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    A properly installed parallel system would have valves on the inlet AND outlet piping so you could shut both of them to isolate the heater. Once that is done, NOTHING that happens in the heater can impact the rest of the plumbing. Before restoring it to service, the heater would have to be drainded, flushed, and refilled with fresh water. But, other than standby losses, you only heat the water you use, so leaving both heaters in operation will NOT substantially change, if at all, your utility bill.
  6. jacdela123

    jacdela123 New Member

    May 7, 2014
    Houston, TX
    i just want to bump this coz i have question.. will the hot water from tank1 (operational) go inside tank2 (the tank that has been shut off)?

    i asked because i'm confused, there is pressuere in tank1 so hot water will go out but can it go tank2?
  7. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    If the cold on #2 is closed, you will not get significant hot water going into #2.
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