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Hot water circ systems

We install a lot of hot water circulating systems in the new homes we plumb. People hate to wait for hot water at the kitchen sink and master bath and these systems work great.

The problem: We've had some customers that want the water heater at 140 degrees to keep down bacteria growth. We'll put in a tempering valve at the water heater to reduce potential scalds. But as the water circulates through the return line and through the water heater it gradually reaches 140 degrees if no one is using any hot water in the house. The tempering valve doesn't draw any cold water in this situation.

When someone opens a faucet there's a spike of 140 hot water until the tempered water gets pulled in.

Any ideas?


  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    You could

    use a timer on the re-circ pump and have it run for a few minutes every hour, or a simple strap-on aquastat to shut the re-circ off when the water temp hits 125* at the pump.

    Hope this helps.

    Mark H

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  • shawn
    shawn Member Posts: 2
    Recirc pump

    Is this a theoretical problem or is it something you are experiencing?
  • John@Reliable_2
    John@Reliable_2 Member Posts: 104
    Yep, what Mark said!

  • That's a real concern.

    Pipe it like you would a radiant mixing valve and a boiler.

    Like this. Flow can get to both mixing valve ports, so mixing still occurs, and elements last longer. Put in check valves and an expansion tank, to keep the cold, COLD, and to keep the water off the floor under the relief valve.

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