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Water heater expansion tank.

James Day_2
James Day_2 Member Posts: 191
What is the proper way to charge a expansion tank on a indirect water heater.

Thanks James


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Follow the manufacturers instructions...

    and if my memory serves me correctly, it states that the diaphragm should be charged to the same pressure as the minimum operating pressure of the system, with ZERO water pressure on the tank. In other words, charge the diaphragm BEFORE you install it.

    This way, any pressures generated by the expanding water will be absorbed by the tank and keep the pressure well below the relief valve setting.


    There was an error rendering this rich post.

  • meplumber
    meplumber Member Posts: 678
    I should probably read the instructions.

    James, I have been charging them to 60 PSI for city water and 40 for well water. We have highly fluctuating water pressure here in the few areas with city water. We have found that we stay out of trouble at 60 PSI.

    I think I will re-read the instructions on one.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Did any one ask...

    ... if the expansion tank is on the boiler side of the indirect, or on the domestic side?
  • James Day_2
    James Day_2 Member Posts: 191
    expansion tank

    Its on the domestic side
  • BobbyG
    BobbyG Member Posts: 79
    doesn't matter - domestic or heating

    If you follow manufacturers instructions (like ME said above) then it wouldn't matter.

    Set at minimum operating - then you have the correct amount of expansion room in the exp. tank.

    If you did it like MEPlumber (for domestic) - that would work most of the time, but maybe not always - if the operating pressure were higher than 60# - less expansion room - relief valve go poppy or weepy, weepy, weepy every hot/cold cycle.

    Big issue.
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