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Old 04-25-2016, 11:51 AM   #1
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Hot water cross over mystery


Hello All,

About 2 weeks ago our hot water started getting less and less hot, now it is completely cold. If I turn the cold angle stop off at the sink, so only the hot water line can feed the faucet, and turn it on, water flows. If I turn it to the completely hot setting water flows, but if I turn it to the completely cold setting the water stops. (No crossover in the faucets). Here is the tricky part, if I turn off the feed to the hot water heater, with only the hot anlge valve on and the faucet on hot only, the water will still run. This happens in all of my sinks except one. In the hookup closest to the hot water heater, if I hook the hose to the hot water angle valve and turn it on, HOT water flows out. If I then turn off the supply to the hot water heater, the flow stops (as it should). Only this one sink functions this way. When this is happening I can hear the water being taken out of the hot water heater, and new water being put in. When I turn on any other faucet it is not even trying to draw water out of the hot water heater, even if I have the cold angle valve on the faucet turned off (so it can only draw from the hot circuit). Also, I turned off the angle valves to the dishwasher and washer/dryer for all the tests.
To summarize, the faucet closest to the hot water heater works flawlessly. All other faucets will only run cold. When the cold water angle valve is turned off (so the faucet can only draw from the hot circuit), and the faucet is turned onto hot, water runs, but is cold, and is not even trying to draw from the hot water heater. Everything seemed to work fine 2 weeks ago, and no plumbing has been tampered with.

PLEASE HELP!!!!!!
Thanks Will
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Old 04-25-2016, 01:00 PM   #2
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Re: Hot water cross over mystery


Welcome to the forum Maroon.

What type and brand of faucets do you have? Single handle, dual handle? Some single handled moens are known for crossover effect.
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Old 04-25-2016, 01:30 PM   #3
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Re: Hot water cross over mystery


They are single handle, not sure on the brand, but it happens with them completely shut off under the sink as well. Also, if I only allow the cold line to enter the faucet, then turn the faucet to hot, no water comes out. I don't think that is the problem. I also replaced the cartridges in the showers to be sure.

My newest theory is a failed anti-sweat valve under one of my toilets. Going to check that when I get home from work today.
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Old 04-25-2016, 09:15 PM   #4
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Re: Hot water cross over mystery


Quote:
Originally Posted by maroonw View Post
Hello All,

About 2 weeks ago our hot water started getting less and less hot, now it is completely cold. If I turn the cold angle stop off at the sink, so only the hot water line can feed the faucet, and turn it on, water flows. If I turn it to the completely hot setting water flows, but if I turn it to the completely cold setting the water stops. (No crossover in the faucets). Here is the tricky part, if I turn off the feed to the hot water heater, with only the hot anlge valve on and the faucet on hot only, the water will still run. This happens in all of my sinks except one. In the hookup closest to the hot water heater, if I hook the hose to the hot water angle valve and turn it on, HOT water flows out. If I then turn off the supply to the hot water heater, the flow stops (as it should). Only this one sink functions this way. When this is happening I can hear the water being taken out of the hot water heater, and new water being put in. When I turn on any other faucet it is not even trying to draw water out of the hot water heater, even if I have the cold angle valve on the faucet turned off (so it can only draw from the hot circuit). Also, I turned off the angle valves to the dishwasher and washer/dryer for all the tests.
To summarize, the faucet closest to the hot water heater works flawlessly. All other faucets will only run cold. When the cold water angle valve is turned off (so the faucet can only draw from the hot circuit), and the faucet is turned onto hot, water runs, but is cold, and is not even trying to draw from the hot water heater. Everything seemed to work fine 2 weeks ago, and no plumbing has been tampered with.

PLEASE HELP!!!!!!
Thanks Will
This sentence in the above paragraph probably is your problem. "Here is the tricky part, if I turn off the feed to the hot water heater, with only the hot angle valve on and the faucet on hot only, the water will still run."

Seems like there is a cross over or the above would not be true. Cross overs usually involve a mixing valve. Locate all instances of mixing. Your water heater is also suspect if you have changing pressures on the water coming in from your meter. Lower pressure of incoming water could cause hot water to flow back up through the cold side if you have an older water heater. Also when you say you turn certain valves off, unless these valves are ball valves you can not be certain the valves stems are closing the gate or opening it. So valves are suspect if they are not ball valves. Do you have a mixing valve under your lavatory sink? Send more information as you try to solve this and someone will help you if you are clear about what the problem is. Good luck.

Last edited by srloren; 04-25-2016 at 09:29 PM.
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Old 04-29-2016, 06:14 AM   #5
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Re: Hot water cross over mystery


I am not a plumber and I think I follow your details. Is there any possibility that someone turned off an isolation valve? I would start at the water heater and follow the hot pipe. You say that the sink closest to the water heater operates as it should, but the ones further down the line do not and they do not draw water from the water heater. That seems to indicate that a valve is closed on the hot pipe between the first sink and the next one. The only other possibility i can think of is that you have a pressure balancing faucet(s). I am not sure how those work, but plumbers gere ciuld probably explain them. I remember that in one of my properties, when my plumber ran all new lines, there was a very slight leak in the hot pipe supplying the tub. I turned off the hot isolation valve behind the tub and called the plumber to come back to fix it. I was doing some cleaning and tried to fill a bucket with cold water from the tub, but when i turned the faucet on, nothing came out, even though i had NOT shut the cold isolation valve. The plumber explained that sunce the faucet was a pressure balancing type, it sensed that there was no pressure on the hot side, so it would not allow cold water to come out.

I dont know if any of this helps you. Hopefully plumbers here can figure it out.

Sent from my LG-D415 using Tapatalk
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