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Expansion tank mounting.

Santa_Bob Member Posts: 5
I have 3 Apts in my building, thus 3 boilers in my basement. All 3 boilers have the tank mounted upside down, as in the picture below. All I can find is conflicting advice, is this OK or not? Some say you should never mount one like this, others say it is fine, as long as it is supported. it originally had an Extrol #15, and it was replaced once already. I believe it was under sized to begin with, and I am replacing it with a #30. The #15 documentation didn't explicitly say you couldn't mount it this way, but the #30 docs say to only mount it right side up. I have been told I can safely ignore this and others say No. So, opinions or comments?

Also, if you would flip it, how would you pipe it? Would you add a air separator? Etc...



  • HomerJSmith
    HomerJSmith Member Posts: 2,408
    It appears to me that you are pumping into the expansion tank, a no no.

    The Radiant #60 tanks are configured this way.
  • kcopp
    kcopp Member Posts: 4,396
    "upside down" is fine.... not the end of the world.
    HVACNUT Member Posts: 5,760
    That position is fine.
    The larger tanks that sit in the floor have a bottom inlet so...
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Although the position is fine, replacing it would be a major PIA.
    With some re working, I'd start from the top of the boiler, up about 1', 90° to the right, another foot of pipe, then air eliminator, iso valves, circulator, then back to the copper.
    Pipe the exp tank off the bottom of the separator via a Webstone Expansion tank valve and either support the pipe (you'll be doing it anyway for the circulator, or use an expansion tank bracket on the wall.
    Then you're done forever with potential problems, and changing/checking the charge for the tank becomes a breeze.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,606
    edited March 2020
    There is no danger in putting the tank upside-down. The tank diaphragm is designed to hold the weight of the water pressing against the air pressure on the opposite side of the diaphragm. By installing it upside-down the diaphragm will flex differently. This will cause the diaphragm to fail sooner than later if installed correctly. How much later? Not sure... my Extrol 30 is 28 years olds and just adding a shot of nitrogen every 3 to 4 years during maintenance keeps it at the 12 psi needed to operate without any problem. I also operate my relief valve at least once a year. I’m on my second PRV in 28 years.

    I do believe I replace more upside-down diaphragm tanks than right side up tanks

    Ed the Heaterman

    P.S. I like @STEVEusaPA’s idea if you are inclined to pay for the repipe. Or have the needed fittings ready for a future service call that requires the boiler to be drained. Then you can get both jobs (the repair and the repipe) completed at one time
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics