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Thurman 09-12-2009 11:21 AM

Hot water in cold faucets
So, I'm visiting my daughter in Fairbanks, AK. She owns a duplex unit here she rents out and there is a problem in it she asked me to look at. In all faucets, kitchen, bath, when you turn on the cold water, hot water comes out for about two minutes before cold water will eventually start coming out. The use boilers up here for heating and to make hot water. I am not familiar with these, being from S. GA. at all, so I tell her to call the local service company. Late next week is the first available service date. Each unit is occupied. I look at all this conglomeration of piping and I see a check valve that in all my experiences tells me might keep the hot water from backing into the cold water lines. Could this be the problem? Thanks, David

JDC 09-12-2009 12:52 PM

Could be that the check valve has gone bad (be it a spring or swing check). If there is a circulating pump, and I suspect there is, and the check is bad, hot water could very well be being introduced into the domestic cold water supply.

concretemasonry 09-12-2009 01:48 PM

Hot water in cold faucets
Back to back duplex with reversed floor plans?

If so, one thing to look at a lazy or dumb plumber that did not realize you have to reverse the supply on one unit/side or the other.

That can be fixed.


plumber Jim 09-12-2009 02:13 PM


Originally Posted by concretemasonry (Post 326891)
Back to back duplex with reversed floor plans?

If so, one thing to look at a lazy or dumb plumber that did not realize you have to reverse the supply on one unit/side or the other.

That can be fixed.


That would just make the hot and cold reversed. He has hot water bleeding into his cold. I would feel both sides of that check valve and see how far the pipe stays warm past the check then turn the cold on and see if it cools. if it does then you do have a bad check valve. also if you have a tempering valve that could do the same thing.

Thurman 09-12-2009 09:13 PM

"concretemasonry"-They do things different in Alaska, this is one unit over the garage and the downstairs unit. They call it a duplex, I call it two apartments, it doesn't matter. Both units have this same problem, and are fed from a common boiler system. "plumber Jim", we went over today to remove things from the garage and that is exactly what I thought to do. The pipes before and after the (as described on it) "backflow prevention device" were both hot as haides. The thermometer on the unit for the hot water was reading 180* at the time. I had my grandson go the farthest faucet from the boiler unit and open the cold water faucet in the sink and it ran for almost three minutes before I felt cold water after the BPD, on the side the arrow was pointing to. About one minute later he hollered he had cold water at the sink. The boiler never kicked in, no pump came on either. Now I know the unit is less then one year old and may be under a warranty. Now I also think I know why I was invited up for a visit- -to handle this and a few other things for her. Thanks for the tips. David

Thurman 09-18-2009 10:29 PM

The repairman comes over today to look into this problem. He turns on the cold water in each sink, bath/kitchen/ both units and sure enough there is enough hot water to take a good shower before cold water comes out. Of course he just looks wide-eyed and says Hmmm. Then he goes to the boiler and starts tracing water lines. Something new to me here: HOT water comes from a water heater that uses a heat exchanger within the hot water tank. The heat to the exchanger comes from the boiler, now I understand how this works. We just don't use these in the South. He finds that on the cold water line going to the water heater there is no check valve, which would let hot water back up into the cold water lines to all of the faucets. Bad installation. He won't admit this as he didn't put this particual unit in, although the company he works for did. Problem solved now. Problem Monday with the heating company on the quality of their work and the warranty to me. Thanks, David

plumber Jim 09-19-2009 10:27 AM

glad to hear you have it fixed now.

AllanJ 09-20-2009 09:13 AM

Water would have to be circulating to get really hot in the cold water pipe just before the faucet. Are these one-handle faucets where perhaps water is crossing behind from the hot line to the cold line with the faucet turned off? (That's a defect but not if you turned off the shower from above leaving the faucet handles open.) The cold water pipe could get a little warm running juxtaposed with the hot water pipe through the walls, though.

With no commingling via circulation, the portion of water still in the cold pipe and coming out first when you turn on just the cold faucet can't be that hot.

If water backed up out of the water heater, it would go back towards the well or water main. Then you would get cold, then a slug of hot, then more cold when you turned on the cold faucet.

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