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Replacing expansion tank

gazzerp Member Posts: 14
I'm experiencing the same percolating issue with my Buderus G124X as described in <a href="http://www.heatinghelp.com/forum-thread/98918/Percolating-Buderus-Boiler">http://www.heatinghelp.com/forum-thread/98918/Percolating-Buderus-Boiler</a> and am going to replace the expansion tank to see if that addresses the issue.  I came to this decision after allowing the boiler to cool-down (to ~100) then tapping the tank: it sounds muffled all over, whereas I believe it should "ring" (on the lower half, at least.)

The tank is an Amtrol 30 attached to a Taco air scoop upon which a Caleffi HiVent is installed, and located on a horizontal trunc line above the boiler.

Can I replace the tank without having to drain the system, if I first close every shut-off/isolation valve I can find (including the cold water supply line) and allow the boiler to cool down (to ~100?) I think I should expect some (minor) water discharge -along with an air "pop," assuming the bladder has any air left in it at all- when removing the current tank but, wanted to seek qualified guidance before going any further.

Thanks in advance...


  • RJ_4
    RJ_4 Member Posts: 484
    exp. tank

    Unscrew the blue or plastic nut on the bottom of the tank and check for air with a tire guage, if water comes out than the diaphram in the tank is ruptured. check this before changing exp tank. You may have air in your system, find a high point and see if you can bleed any air , also check the auto air vent to see if it is possibly pulling in air.
  • gazzerp
    gazzerp Member Posts: 14

    RJ - thanks for responding...

    Neither air nor water emerged... tried first with a tire guage then, the tip of my needle-nose pliers.  The pin inside the valve stem was very firm to the touch so, I didn't want to push any harder.  By comparison -and as I'd expect- the new tank hisses with barely a touch...

    As for the auto air vent: it was replaced two years ago - along with the anode in the HW tank and pressure relief valve (entire system is now 12 years old.) I understand that doesn't mean it's still working satisfactorily but, seeing that I already have the new expansion tank on-hand -and the existing one appears to be faulty- I'm going to assume for now that the Caleffi is okay.

    So - may I return to the question I posed in the last paragraph in my original post: in replacing the tank, can I avoid having to drain the boiler by closing all valves/supply line?

  • SWEI
    SWEI Member Posts: 7,356
    edited March 2013
    tank valve

    Could just be a bad Schrader valve.  Try replacing the stem.
  • RJ_4
    RJ_4 Member Posts: 484
    exp. tank

    As you said get water temp. down, below 100 dg.  this will keep you from getting scalded. A flooded exp tank will be very heavy, I recommend a second set of hands, if that is not possible than support the tank with a pre made box or rigging. The last one I did I shut off the fill valve (make sure it is a possitive shut off ) I lowered the press. to about 2 psig. I had the threads on the replacement tank pipe doped or taped. I also had a inside threads of a ball valve doped. you will also need a close brass nipple on 1 side of ball valve.  I unscrewed the tank ( it was very hard to hold on to due to the weight)   and immediately screwed on the ball valve, I now had time to install the new tank, Doing it this way kept air out of the system.  Keep a shop vac,lots of rags and a plastic garbage can at the ready, you and the equip rm. will get a little wet. the alternative is to drain all press. which usually results in air in the system.  I would only do this If you are an experienced pipefitter or plumber
  • RJ_4
    RJ_4 Member Posts: 484

    Check your local boiler or plumbing code to see if you can install a valve before the x-trol tank
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,491

    Retired and loving it.
  • chapchap70
    chapchap70 Member Posts: 139
    Before you remove extrol

    Close the valves (supply and return) to the system and before the boiler feed valve and drain the water in the extrol tank area to just about zero.  If you have a 0-20 psi pen (tire) gauge, check the extrol pressure when the boiler pressure is at zero.  You cannot get an accurate reading of the extrol tank with the system charged because it just measures the system pressure. 

    If there is say 5 psi in the extrol tank with the boiler area at or near zero psi, you can pump up the extrol tank to what you want your system to run at plus 1 or 2 psi.
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