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Expansion Tank: does 2 = 1 + 1?

It seems that my system needs a rather large (50 litres) expansion tank, for which I don't really have room. Is it possible to use, instead, two 25 litre tanks? In parallel? In series?


  • Ironman
    Ironman Member Posts: 7,379
    In parallel, but connected at the same point to the system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Jamie Hall
    Jamie Hall Member Posts: 23,428
    And be certain that you have as nearly as possible exactly the same air pressure in both tanks.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    delta T
  • Gordy
    Gordy Member Posts: 9,546
    Yes with the above requirements, and installed so the circulator is pumping away from them, and on the supply side of the boiler.
  • Steamhead
    Steamhead Member Posts: 16,889
    What Ironman, Jamie and Gordy said. We've done it.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Gordy
    Gordy Member Posts: 9,546
    I would have to rephrase the supply side of the boiler. Since some modcons like to be pumped into the boiler, or return side of boiler.