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Thread: installing expansion tank

  1. #1

    Default installing expansion tank

    how hard is it to install a expansion tank on a hot water heater. i had a plumber tell me it was self piercing and others said need to put a T in line . can anyone tell me how to install it? thanks

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    The expansion tank does not go ON the hot water tank, it can go anywhere in the system after the prv that is convenient. Since the pressure basically is the same anywhere on the house side of the prv, find a place where you can place it where you have easy access to check it. I've only had a limited experience with the things, but my first one lasted about 12 years. Took me all of about 10 minutes to unscrew the old one and install the new one and (if I remember, maybe about $20). Because of the diameter of the things, I didn't need any tools to unscrew or install the new one - you have enough leverage to do it by hand (at least I did). The best way to do this is to install a brass tee in the water line, a shutoff, then the tank. The shutoff makes it really quick and easy to replace when the time comes.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default tank

    If a plumber tells you they are self piercing, get a different plumber because he is not one.

  4. #4
    Master Plumber master plumber mark's Avatar
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    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
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    Talking maste plumber mark

    buy a big one, its always better to get one that is oversized. big.

    and it gives you lots more expansion room

    what I have read in the actual instructions on the tank themselves, it seems to be best to install one on the cold line comming into the water heater...

    one reason is the heat, I suppose it lasts longer if it is not exposed to constant high temps...even though you see them on boilers.

    test your water pressure comming into your house with a guage during normal hous of the day...

    if it is around 80 lbs psi during daylight hours, that measn it will probably spike to 95-110 lbs at night, or even higher..

    you can check the pressure at 2 am if you really want to get a real feel for your pressure range in the neighborhood.

    its best to pump up the tank bladder to lets say 90-100PSI

    what I understand is the excess pressure from the water heater heating at night or durning the day will push against the internal bladder
    when the pressure ever rises above 90 lbs...

    the larger the tank you buy the more water vloume it will absorb from the system.

    they do seem to work pretty well this way...


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