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Expansion tank that can handle more heat

CBRobCBRob Member Posts: 179
A home that I manage has a poorly placed expansion tank, it's on the cold side of the tank but close to a recirc pump that keeps it too hot.

I'll probably try to put a little heat trap loop before the tank but I'd like to know if there are dhw tanks that can handle more heat


  • JUGHNEJUGHNE Member Posts: 6,896
    How do you know it is getting too hot?
    Most true DHW exp tanks are rated for pretty high temps.
  • ZmanZman Member Posts: 5,827
    DHW expansion tanks can handle more heat than the occupants or the relief valve. What are the symptoms?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • CBRobCBRob Member Posts: 179
    edited November 2019
    Just replaced it last year and it is full of water already.
    I'll take a pic tomorrow of how it is situated
    I'm guessing the failure is heat related...
    Could be something else.
  • STEVEusaPASTEVEusaPA Member Posts: 4,134
    What’s your incoming water pressure?
  • CBRobCBRob Member Posts: 179
    I have not put a gauge to it, but there is a regulator with a 65psi high end.
  • JohnNYJohnNY Member Posts: 2,442
    DHW expansion tanks are typically factory pre-charged to 40 PSI. Isolate and pump up your tank's air pressure. Problem solved.
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    John also oversees mechanical installations and maintenance for metro-area clients with his family's company, Gateway Plumbing and Heating along with his brother/business partner.
  • DZoroDZoro Member Posts: 1,035
    What model of tank are you using? Is this on the domestic water? Boiler water? There are differences between DHW tanks and Radiant heating tanks.
  • CBRobCBRob Member Posts: 179
    John was right, I just needed to pump it up.
    It's at 50 psi now and holding air.
  • CBRobCBRob Member Posts: 179
    I found the tank on the radiant heat was incorrect... same house.
    Swapped in a rx30 .

    Also noticed the circ pump installed with a vertical shaft, but I think that is ok with adequate psi in the system. I saw another discussion here at heating help that talks about pumps installed incorrectly
  • CBRobCBRob Member Posts: 179
    Can I use the flex2 dhw tank that I removed in another dhw application?
    It's not fubar from being exposed to glycol?
  • Jamie HallJamie Hall Member Posts: 12,848
    CBRob said:

    Can I use the flex2 dhw tank that I removed in another dhw application?

    It's not fubar from being exposed to glycol?

    No. Once it has been exposed to glycol, you mustn't use it for domestic (drinking) water.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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