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Expansion tank on Return side?

Hey_Obie Member Posts: 66
Most hot water boiler systems that I have seen have the expansion tank on the supply side.

I read an article that said it is better to have the expansion tank on the return side primarily to help with bleeding the system that has monoflow fittings (which my system has).

So I am thinking of putting the expansion tank on the return side. Any comments appreciated.


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I am a homeowner, not a contractor.

    If you put your expansion tank on the return side, you will need to put the circulator to the boiler between the expansion tank and the boiler.

    You will still want your air separator as close to the output (on the supply side) of the boiler as possible, because you want the greatest temperature water to go through there. On the other hand you will want the air separator just before the circulator because you want it to be running at minimum pressure to help the air out.

    It seems to me altogether to put the expansion tank, air separator, and circulator all on the supply side.

    Do you have trouble bleeding your system? You probably need to do that only once, where you want the air separator to work all the time.
  • Slimpickins
    Slimpickins Member Posts: 339
    Try reading this....

    Pumping Away by Dan Holohan, it will tell you all you need to know. Just go to top of page and click, Shop. Then go to books and browse until you find Pumping Away, Click and then order and you're set!
    STEAM DOCTOR Member Posts: 1,968
    page 41-page 46

    discuss the reasons to avoid putting the tank on the return. the book is a gold mine any will pay for itself the first time you run your system
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    Return Side

    I read that once my self ... I believe ME from the wall posted it once ...Mark picked it up from a European mechanical article or his travels abroad ... It gives a little extra low pressure zone to help release air from the water before approaching an air scoop ... It should be located between the boiler and zone branches ... Diaphragm tanks need to be hanging down and kept wet for longevity .
    I have enough experience to know , that I dont know it all
  • Hey_Obie
    Hey_Obie Member Posts: 66
    Ordered the book

This discussion has been closed.