How to Test for Hot/Cold Water Crossover

Discussion in 'Water Heaters and Softeners' started by aln, Oct 4, 2019.

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  1. Oct 4, 2019 #1

    aln

    aln

    aln

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    I just had tankless water heater installed, and am not getting very hot water; is is 109 degrees but heater is set for 135 degrees, Installer clams it is because of crossover at one or more fixtures. How do I check for crossover?
     
  2. Oct 6, 2019 #2

    jeffmattero76

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    Before the tank less was installed, did you have the same problem?

    If not, and assuming that the only plumbing work that was done was removing the old water heater, and connecting the new, any crossover would have to be in the new piping that that same installer installed.
     
  3. Oct 6, 2019 #3

    RenewDave

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    Man I make so much money with this exact problem. Was it tankless for tankless switch, or tank for tankless switch? Recirc? Brand? Soo many possible problems. First, turn off the valves at the HWH and see if you get ANY flow from ANYWHWERE in the house from a hot side fixture. There should be NO flow from the hot side. If you get flow, even a little, you have problems. That’s a start.
     
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  4. Oct 9, 2019 #4

    aln

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    We were getting crossover before, but only at one shower valve. This installation is in a 4 unit 2 bedroom, 2 bath complex. No other cross over ever noted at any of the other fixtures. Since then, I had the cross over shower valve replaced.
     
  5. Oct 9, 2019 #5

    Diehard

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    Did you check the water temperature coming out of the tankless water heater?
     
  6. Oct 9, 2019 #6

    aln

    aln

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    I have not. How do I do that?
     
  7. Oct 9, 2019 #7

    jeffmattero76

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    With a thermometer like the kind you might have in your kitchen for meats or for candy. Measure or at the faucet that is closest to the water heater.
     
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  8. Oct 9, 2019 #8

    aln

    aln

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    It was a tank for tankless. There has always been a recirculating system with the tank setup. Tankless is two Rinnai RUR199iN taped into the existing re-circulation line.
     
  9. Oct 10, 2019 #9

    aln

    aln

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    Temp at closest faucet is 109; tankless (Rinnai RUR199iN) is set at 135. Installer says that is because of cross over at one or more faucets in the building.
     
  10. Oct 10, 2019 #10

    Diehard

    Diehard

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    Don't know exactly how things are arranged there but can you shut off the recirculation loop?
    What I'm thinking is trying to get a better idea if the water heaters are actually putting out the temperature required without being affected by the recirc loop.
    Isn't there a hose connect on the hot water line coming out the bottom of the unit that can be used for verifying temperature?
     

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