Hot water on dedicated recirculation line

Discussion in 'Water Heater Forum, Tanks' started by MachAF, Jul 29, 2021.

  1. MachAF

    MachAF New Member

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    Jul 27, 2021
    Location:
    PNW
    When I run hot water without the recirc pump on it takes a while to get warm but it never gets truly hot. Let’s say it feels like only 100f. When I turn the pump on I will get hot water (120f). Any ideas why that is? Is cold water mixing with the hot some how? I didn’t think it did that with a dedicated recirc line.

    thanks!
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
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    New England
    You need a properly working check valve on the return line, otherwise, when drawing hot, it can come from both the hot supply, and the return line which is normally plumbed into the bottom of the tank, so is typically the coolest area of the tank, or will be once you start using hot as that's where the cold goes.
     
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  4. MachAF

    MachAF New Member

    Joined:
    Jul 27, 2021
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    PNW
    That makes sense! I never thought it like that. Thanks!
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    FWIW, some pumps can be had with a built-in check valve, but it's not that hard to put one inline where you have access, and, if there's more than one branch on that return line, make sure to put the valve where it can handle both sides or use more than one.
     
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