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Expansion tank in attic

MikeF Member Posts: 2
New homeowner (almost) - close next week - trying to understand system in place.  Looks like 2 pipe steam radiators but I just got thrown off finding an appox. 15 gal. expansion tank in the attic.  What is an expansion tank doing in the attic and is this steam or hot water?

Please remove the blinders from in front of my eyes. 

Much appreciation,



  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Gravity hot water system

    If you have an expansion tank in the attic, it appears that you have a gravity circulation hot water system. These were popular before the 1930's and used the differences in density of heated water to produce circulation in the system instead of an electrical pump.

    What does the boiler look like in the basement? Are there large diameter iron pipes directly connected to the top and bottom of the boiler or has a pump been added to convert the system to forced circulation?
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