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Hot water out of cold taps - plumber is stumped

Posted by bustergordon (My Page) on
Mon, Aug 23, 10 at 12:22

Hi everyone! My husband and I bought a home about a month ago, and we immediately noticed that there was hot water coming out of the cold taps in the master bathroom. We had the plumber come out, and he is flummoxed. He simply can't find the cause. He's checked the cartridges for each of our single handle faucets and showers, but none of those is the culprit. He crawled under the house and determined that there isn't a plumbing issue - the cold water is cold under the house and the piping doesn't seem to be the issue. He is now proposing to cut holes in our walls to determine if any of the showers has a failed mixing valve which could be causing this.

My question is: is there anything else that we should be thinking about before my walls turn into swiss cheese? Our home inspector did note a couple of things, but I'm not sure that they're relevant (my plumber doesn't think so, but other opinions would be welcome):

* there is corrosion on the check valve for the recirculation pump for my hot water heaters (which the inspector said indicated leakage)

* there are separate temperature/pressure valves for each water heater (I have 2 water heaters in series), but the drain pipes are connected together

* there is no expansion tank (the report notes that certain recirculation systems require an auxiliary expansion
tank to relieve excess pressures from the tank)

Could any of these be the problem? What else should I be thinking about?


Follow-Up Postings:

RE: Hot water out of cold taps - plumber is stumped

Just a thought. Any crossover valves anywhere that might be open or leaking? Laundry tubs....water softener?

RE: Hot water out of cold taps - plumber is stumped

Turn off the cold water into the water heater and test the taps.

If all are cold there is a crossover somewhere.

Finding one can be a real adventure.

RE: Hot water out of cold taps - plumber is stumped

We're having this problem in our small apartment building. In our case, it has only recently arisen.

In the past, when we had this problem, there was a check valve to the recently-replace water heater that had been installed backwards.

I've been wondering if our new problem is caused by a failing check valve down near the water heater.

But your comments have me curious--so I have some questions about all the possible causes of such a problem.

*can it be caused by a single-handle faucet being installed incorrectly?
*can it be caused by a bad cartridge of a single-handle faucet?
if it is, will it mostly cause the problem close to the actual faucet itself?

(I'm the only unit apparently experiencing this problem; so I'm wondering if it's possible that the problem is in my newly installed single-handle faucet)

*Can it be caused by a failed mixing valve inside the walls?

RE: Hot water out of cold taps - plumber is stumped

Remove handle, turn cartridge 180 with a wrench, put the handle back on and see what happens. That solved it for me one time, but I don't recall which brand. Might have been an old Moen chateau.


Sorry, forget about what I wrote. I should have read more carefully.

sensor valve?

Isn't there a crossover used when a hot water recirculator is used? Maybe there's a bad sensor valve? Here's some Watts Premier literature, if that's what you have.

RE: Hot water out of cold taps - plumber is stumped

My condo has recently notified owners they should only install hot and cold knob type fixtures when doing replacements from now on. Any water problems found impacting on others that trace back to an owner's newly installed single lever fixtures will now have the cost of finding same charged to the unit involved.

RE: Hot water out of cold taps - plumber is stumped


I've looked at a few places online, as well as at the info for my own single-handle faucet, and they all imply that you ought to be able to change the cartridge WITHOUT opening the wall. You just have to take off the escutcheon and the handle.

Laat2--I wondered if my small co-op would institute that restriction.

But it seems silly to me. Of course I'd have to pay for that sort of repair, whether I lived in a single-family house or a co-op. And in my building, the hot water is set SO hot (in order to get the heat to the upper floors) that our single-handle faucets are actually crucial to people's safety. They're more likely to get burned by turning on one knob, or by finding it hard to tell how much hot water they've got going into the mix. We used to have the two-handle faucets, and it was a major pain.

And I've had this faucet for several years, and this is the first sign of a problem. I'm not even convinced it's the source of the problem yet. and, it's easily fixed.

In our building, we'll deal with it by simply asking people to investigate their own unit. Or we'll say, "If this happens, everyone has to change the cartridge on their single-handle faucets."

RE: Hot water out of cold taps - plumber is stumped

"Isn't there a crossover used when a hot water recirculator is used?"

Not if you have an actual recirculator system, as opposed to one that puches cooled off hot water back into the cold lone.

The Watts system posted is one of the 'sorta' systems.
It pushes cooled hot water back into the cold line.

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