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Hot water

Bob Forand
Bob Forand Member Posts: 305
Well now I am stumped...Can someone please help me with this teaser ? I swapped out a boiler last week and the HO asked me if I could take a look at a problem he is having. He is getting hot water at the faucet when he turns on the cold tap.

Here are the issues:

Warm water in all toilet tanks ( 3 floors, 3 baths).
Hot water at every tap.
Has gotten worse as time goes on.
New indirect installed, problem before and after.

Here is what I have diagnosed thus far:

No toilet tank mixing valves.
Isolated washing machine solenoid valve.
I dont believe it could be migration becuase the hot water is at every faucet five minutes later. ( it does go cold after you run the faucet for a bit).
Looked for crossed water lines and could not find any.
No mixing valve on the indirect either.

Any other suggestions ???


  • check any faucets,

    laundry tub?, that may be shut off at the end of the spigot vs the handles
  • Jack
    Jack Member Posts: 1,047
    Had this very problem recently

    Plumber, a good guy installed a new Rinnai and got hot water in some faucets, cold in other HW faucetts. With side by side lavs, one would get hot water and one wouldn't. It was magic. Weird magic, but magic none the less. At this point, just prior to jumping out of that third story bathroom window I went in and turned the shower valve handle and suddenly all the problems were resolved. It was an older Delta with the two "center mount" dials. One was for setting temp and one was for on/off. The unit was cross piped in the wall and had given these types of problems for a long time. Depended upon where the homeowner left the temp dial.

    Beyond that, turn off all the CWS under all sinks and work it back one by one.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,230
    troubleshooting opportunity

    Hello: Is there a recirc line? that can cause problems like you're seeing. Also, test for cross connection by shutting of the cold supply to the heater and opening any hot tap. If it stops running in a few seconds there is no cross connection. If it keeps running, listen at all taps and track it down. I've had problems with Moen and Grohe. A shut off on a showerhead can do the same thing if hot and cold to the shower are left on.

    Yours, Larry
  • bob eck
    bob eck Member Posts: 930

    do they have moen single handle t&s faucets? they can put hot water into the cold side.
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
    Mixing valve?

    Had one in one of my buildings do the same thing. Also can happen with elec. HWH with failed heat traps.
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