Odd hot water behavior - Help!

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Old 03-16-11, 11:16 AM
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Odd hot water behavior - Help!

Hi,

I have a slightly odd situation in our bathroom with the hot water coming from the faucets. I have a single shower faucet with a knob to point towards hot or cold and a sink, again with a single faucet, but with a separate hot and cold tap. We have a problem with the hot water that when turned on, it stays hot for a short while, then runs cold. Turn off the tap for a minute or two and back on again and it stays hot, then runs cold. It is the same behavior for the shower and the sink.

I discovered today that if I put the shower faucet on hot and then run the sink hot water tap, the latter remains scalding hot without going cold. At the same time, the hot water coming out of the shower is cold. As soon as I turn off the shower faucet, the hot water coming from the sink faucet cools right down.

Also, if I put the washing machine upstairs on a cold cycle, the hot water coming from the shower faucet remains scalding hot until the washing machine has completed the initial cycle (filling with water). Oh, and on the cold cycle, the water filling the washing machine comes out hot for the first 20 seconds or so before going cold.

One last thing, I did a test with the shower faucet upstairs. I turned it to cold and whilst that was running, put the shower faucet downstairs on hot. Turns out the behavior is identical to the washing machine. Whilst the faucet upstairs is on cold, the water coming from the one downstairs remains really hot. As soon as we turned off the faucet upstairs, the one downstairs cooled down (as with the washing machine).

I spoke to a plumber and he wasn't sure what could be causing this. Possibly a cross connection somewhere? He is going to 'speak to a few people' and get back to me, potentially with the idea of opening up the walls behind each of the showers (upstairs and downstairs) to get a look at the pipes and see if there is a cross connection somewhere.

I know this is a lot of information, but any help is much appreciated.

Thanks.
 
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Old 03-16-11, 11:40 AM
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Yes you hace a cross connection it seems. There ar only two places this may occur. The shower diverter of a recirc line off the HWH, possibly a check valve.

1. What type of shower diverter? Thermostatic? Model?
2. Do you have a recirc line?

Mike NJ
 
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Old 03-17-11, 07:14 AM
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What brand faucets and shower valves? A faulty Moen cartrige will cause a cross connection.
A recirc. line that is absent a check valve or has a lealing check valve will cause the problems you are having.
Do you have a "splitter" on a laundry faucet that allows you to leave both faucets on but turn the water off at the splitter? How about one of those low flow shower heads that has a button to stop the flow. Any kind of device on a faucet that allows you to leave the faucets on and stop the flow at the spout will allow hot and cold to mix.
 
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Old 03-17-11, 11:33 AM
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Hi,

Tested it with the washing machine valves turned off, but same problem. Here is a simplified recap of what is happening:

* turn shower faucet upstairs on hot - water comes out hot then goes warm - i leave this running for the entire test below...:

* turn on bathroom shower faucet downstairs on hot - remains very hot whilst shower faucet upstairs is running - shower faucet upstairs goes cold

* turn on bathroom sink faucet downstairs on hot - remains very hot whilst shower faucet upstairs is running - shower faucet upstairs goes cold

* turn on kitchen hot water faucet downstairs - remains very hot whilst shower faucet upstairs is running - shower faucet upstairs goes cold

* as soon as I turn off the faucet upstairs, all of the faucets downstairs cool down and I have the same problem as before - hot water cooling down.

* one last thing, if I turn off the faucet upstairs and do a separate test downstairs this is what happens:

- put shower faucet downstairs on hot and leave running - whilst running, turn on hot water tap in sink - sink hot water stays really hot and shower faucet water suddenly turns freezing cold

Any ideas? I'm at a bit of a loss. Could it be a cross connection somewhere?
 
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Old 03-17-11, 12:31 PM
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You did not say what brand shower faucets you have?

Anyway it seems like the spools are bad in the shower diverters. I can better help you if I new the brand. They are pressure balanced so when you use water elsewhere the water in the showers will not scald you.

Do you have a recirc line for the HWH?

Mike NJ
 
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Old 10-01-13, 09:05 AM
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Cold Water to Hot Water Cross Flow Fixed

I had a VERY similar problem in my house recently. Tepid water from every faucet or shower on that side of the house that uses that hot water heater UNLESS you turned on more than one shower or faucet. In other words, if the cold water was "diverted" or there was a pressure drop across a device, it would allow hot water to flow through a 2nd or 3rd device.

For example, if I wanted hot water from the kitchen faucet, I would have to turn on a bath spigot and run cold water or run a load of laundry. Yeah, how strange is that? I could only figure there was piping allowing a cross flow between the cold and hot water or there was a bad valve on a device allowing the mix. Also, while changing out my hot water heater last time, I noticed there was still pressure on the vessel even after closing the cold water supply line while draining the tank. That confirmed a cross flow condition.

An inspection under the house revealed no cross flow piping. Next, while running water from the kitchen faucet, we would listen carefully around the Moen shower valves and could here water flowing.

We changed out both Moen shower valves with new cartridges and the problem went away. Hot water from every device now. Yay!
 
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