Cold water coming out of hot tap - problem?

drywall_dan

I am not a plumber. When I close the hotwater outtake valve from the hot water cylinder, I had expected that hot water water would stop flowing from the hot taps/faucets. i.e I expected no water. However, cold water flows instead from the hot tap. If I open the hot water line valve, then hot water again flows from the hot tap. Does this indicate a problem somewhere or is that expected behaviour? If it is a problem - is it one that should be...

Originally asked by Mtl Dev on Stack Exchange (diy) (CC BY-SA 3.0).

uphilltech

Great question — answering as the UphillTech team:

The mixing valve of the washing machine can let cold water into the hot line. Also single valve lavatories and kitchen faucets. You can tell which one is allowing the flow by turning off the cut-off valve to that point of use. EDIT This is only occurring when the hot water line is shut off. It is not a fault condition. It happens all the time with the single handle sink mixing valves.

Full answer by Jim Stewart: https://diy.stackexchange.com/a/111361 (CC BY-SA 3.0).

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