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Thread: Expansion Tank Installation

  1. #1
    DIY Junior Member
    Join Date
    Nov 2009

    Default Expansion Tank Installation

    I want to replace my tank.I keep seeing people say first put a brass tee fitting into the cold water line.I don't have that right now what I have is adapter fitting;because my cold water line where the tank is connected is too big for the tank to go straight in on its own.Is it a problem if I don't have a brass tee fitting and would that be better?

  2. #2
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    I'm not sure I follow exactly what your question is, but maybe this will answer it. The way an expansion tank is installed is with a tee in the cold water line between the PRV and water heater. The tank needs to be supported well, but can be vertical (hanging down) or horizontal. In other words, there is quite a bit of leeway on just where it ends up. From the tee in the water line, there is a copper fitting that comes with the tank that makes the transition, one side screws into the tank and the other side is designed to go into a 1/2" tee. If your tee is larger, then you have to reduce the portion of the tee that goes to the tank. You can use additional 1/2" pipe to position the tank as described above. I would also recommend a ball valve between the tank and the tee to isolate the tank if needed to install a new tank someday.

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

    Default tank

    I have never received any fitting with the tanks I buy, and our water lines are all 3/4" so a 1/2" fitting of any kind would be useless.


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