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Thread: Expansion Tank

  1. #1
    Join Date
    Oct 2008

    Default Expansion Tank

    I have a question regarding the placement of the a hot water expansion tank. How critical is it for the tank to be in the cold side of the system? My hot water installation has the tank in the HOT side of the system. My install is in a real confined area so im sure thats why they installed it that way. If it has to be in the cold side, can it be installed anywhere in the COLD side, such as after the main shutoff for the whole house?

    Thanks in advance for the help.

  2. #2
    Join Date
    Oct 2008

    Default Re: Expansion Tank

    I'm no plumber but my expansion tank, my dad's expansion tank and I believe all of the ones I've seen are on the cold side. The idea being pressure to both the hot and cold water in the house.
    Ray @ http://tanklesswaterheaters-howto.blogspot.com/

  3. #3
    Join Date
    Feb 2008

    Default Re: Expansion Tank

    The expansion tank is positioned correctly---it has to be on the HOT side of the system.

    Water expands ~5% when heated; thus, the purpose of an "expansion" tank is to absorb this extra volume so the pressure relief valve doesn't keep opening to dump water onto the basement floor.

    I assume you're talking about an ET for domestic hot water piping, which usually has a charge pressure listed on it of ~50-80 psi.

    ET's are also widely used for hw heating systems to also absorb the extra 5% volume of heated water & have a charge pressure of 12 psi.

    Check your ET to see if it has its charge pressure listed on it; along with such words as "therm-x-trol" or "extrol" or "fill-trol.

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