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Old Steel Expansion tank

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vicki1990
vicki1990 Member Posts: 2
edited February 2021 in Gas Heating
How do you add air to an old steel expansion tank? The expansion tank doesn't not have an area where I can read the pressure but I do have a compressor and I can add air to it.
I drained water from it today and i opened one of the plugs but it doesn't seem to suck air rather than push it out. Was weird. Perhaps it's an old junk. Thanks for your help


Here is a similar old steel tank I have.

I have one of these guys:

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,867
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    I have done this before
    https://forum.heatinghelp.com/discussion/comment/1620527#Comment_1620527

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • vicki1990
    vicki1990 Member Posts: 2
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    EdTheHeaterMan said:

    I have done this before
    https://forum.heatinghelp.com/discussion/comment/1620527#Comment_1620527

    I have read your post and saw your diagram about the expansion tank; i do not believe my expansion tank SUCKS any air but rather blow it out; I was thinking of introducing air via compressor to it. am I missing something?
  • Jamie Hall
    Jamie Hall Member Posts: 23,330
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    You drain the tank completely empty when it is valved off from your system. Then close the drain and open the valve to the system and bring the system up to pressure. That's all there is to it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    rick in Alaska
  • vicki1990
    vicki1990 Member Posts: 2
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    Jamie Hall said:

    You drain the tank completely empty when it is valved off from your system. Then close the drain and open the valve to the system and bring the system up to pressure. That's all there is to it.

    Hi Jamie! I did that but when I watch some other videos I notice that whenever you drain the expansion tank you would need to allow air back in; once you open that tiny valve, the expansion tank sucks air IN. My expansion tank blow air out; I did what you said earlier but my pressure keeps going back up again, every time I drain the tank the way you said to do. thanks for the help.

    Vicki
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,546
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    @vicki1990

    @Jamie Hall is correct. Just drain the tank when it is completely empty close the drain valve. Open the valve that connects the tank to the system and leave it all the way open. The tank will be full of air and the water will enter. Add enough water from the system fill valve (city water to bring the system pressure to 12-15 psi.

    The tank is supposed to be 1/2 air and 1/2 water which it will be.

    It's not supposed to be 100% full of air


    You only need to drain the tank if it is waterlogged (100%) full of water. If you have any automatic air vents on the system remove them and install manual bleeders

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