Sometimes when I turn on the cold water in my master bathroom sink, warm water flows out of it for about 1 minute until the water turns cold. A minute is a long time to wait for cold water, not to mention the expense.

Numerous plumbers have looked at the house and no one seems to have an answer. One plumber changed the mixing valve in the master shower, but it had no effect on the issue. I'm hoping someone has a solution.

Some info:
The house is in NY. There is a 75 gallon hot water tank. The house has 4 bathrooms and this warm water issue happens in all of them but more so in the master bathroom... which is the furthest fixture from the hot water tank. This issue happens year round. So even when the heat (boiler) is turned off, this warm water issue still happens. Interestingly, this warm water issue never seems to happen at the kitchen faucet, which is on the other side of the house...opposite the hot water tank.

I'd appreciate some help.

Do you have a recirculation system on your hot water distribution?

it's gonna take some detective work to figure out where the water is crossing over.
you'll have to run the cold faucet until it gets cold. then run the hot 'till it gets hot. then go to the water heater and feel the cold inlet pipe. it will be nice and cold. now, wait a while and feel the cold inlet pipe again. it should be getting warm ( not supposed to). keep going back and fell the cold pipe and it will lead you to the point where it is crossing over. this might take a few hours during which no water can be run. so, put on your sherlock holmes hat, be patient and you will find it.
BTW, i just did one of these same jobs. the tub valve is crossing over just as your plumber had guessed was your problem.

An improperly plumbed diverter can cause the problem as well, you may or may not have one.

I am guessing that you have a hot water recirculation system, and if so, SOMEWHERE the hot and cold water pipes are close together. The constant hot water in the pipe then heats a portion of the water in the cold pipe so it becomes warm. When you open the faucet that water is expelled and things are normal until you turn it off and the water becomes stagnant again.

Thanks for the response. No, there is no recirculator.



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Would an improperly plumbed diverter cause this issue to happen at all the bathroom sinks in the house? One plumber that came to my house a few years ago to replace a bathroom faucet told me that the pipes were backwards. Maybe I do have a diverter that is not installed correctly. How would I know?



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every shower diverter starts out cold and the more you turn the handle the hotter it gets.
so, cold thru hot.. if yours start out hot and the more you turn the handle they get colder, they are backwards.

Thanks for your comment Paul48.

The disparaging remarks that you commented about, have been removed by the Plbg Staff.



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NO!!! Therefore, there is nothing for you to know. There are many possibilities, but someone has to be there to test the system, and even then it could take days of on and off testing to decide what COULD be the cause, and whether it can even be fixed.