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Thermal Exp Tank in Place of Well Pressure Tank

Greetings,

Isn’t a thermal expansion tank and a well pressure tank the same tank just used for different purposes? Consider the following:
I suspect I will not get a straight answer on this because I fear the well industry would like to keep this a secret to control the prices of their equipment, namely, well pressure tanks but here goes nothing...

I was given a brand new thermal expansion tank Amtrol Therm-X-Trol ST210V (86ga) leftover from a job site. In as far as I can tell, it is identical to the Amtrol Well-X-Trol line.

My old galvanized air-over well tanks are rusting and I want to replace them.

Anything I should know before doing so?

Thank you in advance

Comments

  • JUGHNE
    JUGHNE Member Posts: 8,261
    Thermal tanks are not protected/coated for fresh water usage, that would be why they are less money. It might last 1-2 years as a well tank.

    Well tanks are protected/coated inside from the corrosion caused by the oxygen introduced with fresh water, that is why they are more money. It might last 5-10 years. BTW the larger the tank, the longer it will last, pay now or pay later.
  • hot_rod
    hot_rod Member Posts: 14,749
    I think the ThermTrol is a domestic HW expansion tank, intended for potable water.

    Possibly the well and ThermTrol tanks may have a different diaphragm material? it has to be a FDA approved product if it contacts drinking water. Maybe not so in hydronic tanks.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    JUGHNE
  • JUGHNE
    JUGHNE Member Posts: 8,261
    I am wrong :o , Hot Rod is right. I didn't read well. I have had a ST on my domestic water heater for 15+ years.

    However a ST diaphragm does not have to contract & expand as quickly as a well tank would. The change in pressure is less and more gradual. That could be where the money difference is.
    I would guess the FDA rating for drinking water would be there for the ST diaphragm as HW is used by some for cooking, ice making etc.
  • rafjr64
    rafjr64 Member Posts: 5
    the term-x-trol and the well-x-trol both have the same butyl bladder and the same polypropylene liner. Both are rated for drinking water. Assuming that is true, go ahead and use the therm tank?
  • JUGHNE
    JUGHNE Member Posts: 8,261
    They may have the same materials, what I mean is the strength/thickness of the bladder could be less for the thermal tank because it was designed for less rigorous flexing. IMO
  • rafjr64
    rafjr64 Member Posts: 5
    Ok. Gotcha. Thank you. Will call the manufacturer and ask them. Appreciate you taking the time to comment.
  • RobG
    RobG Member Posts: 1,850
    It could also be that a thermal expansion tank may have a smaller inlet as the dump load is minimal. The price difference could also be in the certifications required? I know that ASME tanks cost more than non-ASME although the manufacturing process is the same.
  • rafjr64
    rafjr64 Member Posts: 5
    It's Amtrol. They have all the certs. I am wondering if the inside of the steel tank is lined differently on the ST210V vs. the WX-350. The ST210V has a 1yr warranty and the WX-350 has a 7yr. This is the only difference I have been able to ascertain.
  • Jamie Hall
    Jamie Hall Member Posts: 15,726
    They can be used interchangeably, and that is no secret to anyone -- there's no deep dark conspiracy here. What is also no secret is that the tanks designed to control well pumps (and also used for similar purposes) have different interior linings -- not just the bladder, for bladder type tanks. This is part of why the tanks used for drinking water have a seven year warranty. Will a tank designed to control thermal expansion in a system work as a well pump control tank? Yes. Will it work as long? Probably not -- but you might get lucky.

    Be sure, however, that you are staying within the precharge and acceptance volumes.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • rafjr64
    rafjr64 Member Posts: 5
    Thanks Jamie. Appreciate your input.
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