Expansion tank

coolvtJuly 19, 2011

A plumber recently replaced an electric hot water tank in an apt. builing and put in an expansion tank on the outgoing side of the hot water tank. Said this was required in some states. Has anyone heard of this? I figured with the tank having a blow-off valve that it wouldn't be necessary.

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The T&P valve on the WH is not intended to mitigate thermal expansion... it is a safety device.

An expansion tank is required by code in a closed plumbing system to mitigate thermal expansion but it should be installed on the cold supply to the WH not on the hot side.

Make triple sure the expansion tank is installed on the hot side and then call the plumber back to correct his mistake.

You can learn about thermal expansion by clicking here

    Bookmark   July 19, 2011 at 9:47AM
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Guess I learned something new. I will definitley check to see what side it's on.
Thanks, Mark

    Bookmark   July 23, 2011 at 10:52PM
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My plumber also said the expansion tank should be located on the hot water outlet of the WH. While this make sense, since it is the hot water that expands, Justalurker and others have said the tank should be installed at cold water inlet to WH.

Can anyone point me to code(s) or proposed codes(s) to resolve this? I want to have something to show the plumber.

    Bookmark   July 28, 2011 at 11:10AM
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The heated water in the WH expands and that expanded volume is EVERYWHERE in the system and is more easily mitigated on the cold side so the bladder in the expansion tank doesn't have to deal with higher temps than necessary which will lengthen it's service life..

One only needs to look at the installation literature to see the proper place to install the expansion tank.


    Bookmark   July 28, 2011 at 12:35PM
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YOU don't have to show your plumber anything. Simply insist that he place the expansion tank in the correct location, on the COLD side, unless HE SHOWS YOU code specifying differently. He works for you, not the other way around.

    Bookmark   July 28, 2011 at 3:04PM
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