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Old 08-06-2013, 05:18 PM   #46
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Hot water from cold pipes, plumbers are stumped


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Old 08-07-2013, 08:39 AM   #47
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Hot water from cold pipes, plumbers are stumped


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I used my IR thermometer to read the temperatures of the hot and cold water heater connections. I read 110F on the cold line where the WH hose connects to the copper house plumbing, e.g. about three feet from the WH inlet. I'm not sure how much heat ought to be conducted out of the WH pipes, but to me this reading suggests I'm getting significant hot water backflow from the WH into the cold pipes. This implies a cold-water check valve would be effective in stopping the problem, even if this isn't the original cause.

I had intended to try a check-valve "hack" that I read about elsewhere on the Internet: drill a small hole in the check valve's gate, so that a little bit of reverse flow is allowed to handle thermal expansion. My plan was to install such a valve on my cold inlet to the WH to see if this helped our problem. If it did help, I'd go ahead and hire a plumber to do things right with a proper expansion tank and non-compromised check valve. I bought and drilled a check valve, and tried to install it, but I couldn't get the flex hose connectors to stop leaking, nor did the local hardware stores have replacement flex hoses in the right size. So I ended up having to remove the check valve and go back to the prior check-less system.

-Seabeast
So what is the purpose of the Heat Traps you had installed on water heater inlet and outlet piping? These don't work?
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Old 08-07-2013, 09:45 AM   #48
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Hot water from cold pipes, plumbers are stumped


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  • I used my IR thermometer to read the temperatures of the hot and cold water heater connections. I read 110F on the cold line where the WH hose connects to the copper house plumbing, e.g. about three feet from the WH inlet.
On my water heater, the cold water pipe is 77 degrees, measured 3 ft from the WH. 110 seems high.
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Old 08-09-2013, 03:27 AM   #49
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Hot water from cold pipes, plumbers are stumped


Do you have a sprinkler system or a backflow preventer installed on your water service.
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Old 08-10-2013, 12:38 AM   #50
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Hot water from cold pipes, plumbers are stumped


Very interesting problem. I'm not sure of how your system is plumbed. Do you have enough separation between the hot and cold sections?....

Is the recirculating pump on a closed system that brings cooled, unused hot water back into the HWT? Is the pump's internal check valve stuck in a slightly open position because of a spec of sand or grit?

In the first fix did you change the location of cold supply into the tank or is it connected on the T after the recirculating pump? If that's so is it possible that the cold supply before the T needs a check valve?

Maybe the HWT is set at too high a temp warming all the surrounding piping so it doesn't matter if there is a check valve;

Maybe during the new installation some H and C pipes were placed too close or are actually touching somewhere near the new HWT?

Maybe an expansion tank for the cold water supply would help - water in an expansion tank (with a check valve after the expansion tank) would take much longer to heat by surrounding pipes.

Sorry if some of these thoughts were already mentioned by others in previous posts.
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Old 09-14-2013, 08:13 PM   #51
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Hot water from cold pipes, plumbers are stumped


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Originally Posted by drakejohnson View Post
Do you have a sprinkler system or a backflow preventer installed on your water service.
We do have a sprinkler system. The house has a pressure reducer on our main input, which I believe functions as a backflow preventer.

/Seabeast
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Old 09-14-2013, 08:36 PM   #52
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Hot water from cold pipes, plumbers are stumped


Is this fixed yet?
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Old 09-14-2013, 08:57 PM   #53
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Hot water from cold pipes, plumbers are stumped


Sorry for abandoning this thread for so long, since I just know a bunch of you are at the edges of your respective seats waiting for an exciting conclusion.

Anyway, since my last post in August, I hired a plumber to install a cold-water check valve on the input line to the water heater, complete with a thermal expansion tank.

For a few days after the repair, I was pretty convinced this had solved the problem, but my wife kept complaining it wasn't totally gone. Finally I caught it in the act: the water coming from the cold tap of the kitchen sink faucet was too hot to put your hand in, just like before the repair. I've noticed it several times since.

So the bottom line is that after doing the last thing I could think of to fix the problem, we've only mostly fixed it. I'm pretty stumped at this point.

As an aside, all the houses in my development were built with pressure-reducers on their main water inlet, but no thermal expansion tanks. Doesn't that make the plumbing system "closed", and thus really need an expansion tank?

/Seabeast
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Old 09-15-2013, 02:38 AM   #54
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Hot water from cold pipes, plumbers are stumped


Do you have pressure compensating valves. I just redid a bathroom and had some funky things when I only had pressure to one side of my valve. Very little water would come out because of the differential and some hot would move to cold side when under pressure on both sides. I will have to check how much as it is so new I haven't even showered in it but the wife has.

When you are heating the water it expands and pushes through the compensating valve to the cold side and tries to make its way back to the water heater where it will be heated and so on. Using cold such as toilet flushing will drop the cold side pressure obviously and add to the problem.

The circ pump adds just enough pressure to amplify the problem. The expansion tank helps but doesn't solve it.
I have worked in shops with a "Y" hose on garden outlets connected to both hot and cold. If the valves are left open over night the hot will go a long way back into the cold as cold is used in other parts of the building.

I know just enough to be dangerous so take what you want from this but it may be your bridge between sides.

Last edited by Sureshot; 09-15-2013 at 02:42 AM.
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Old 09-15-2013, 01:22 PM   #55
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Hot water from cold pipes, plumbers are stumped


So the answer is to increase the incoming cold water pressure??
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Old 09-15-2013, 02:34 PM   #56
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Hot water from cold pipes, plumbers are stumped


Could it be crossing through your washing machine?
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Old 09-15-2013, 03:18 PM   #57
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Hot water from cold pipes, plumbers are stumped


I would disconnect the cold side at each fixture, wash machine etc and see what happens. If it is at the kitchen sink that is the first place to look. Some thought needs to go into the procedure.

Increasing the cold pressure is not going to help IMHO because the circ pump will always be additive to the pressure. Possibly their is a pressure balance valve but I am unaware of the products available. Possibly a check valve on the cold at the offending appliance or fixture is all it will take.

I know from my remodel that my wash machine valve leaks with zero pressure on the one side. I redid some copper with PEX, replaced the water heater, and had many other things on the go so we were going to run a load of laundry with cold. I had the copper cut. With the machine on Cold only I got water feeding back out the cut Hot line and had to close the valve on the copper stub.

Edit: I was thinking that since the wife has been gone a few days and I have been in the shop I would get a good read on my "leaks". But since we don't have the circ pump all my lines are at room temp on both sides. It may be a bigger issue or non issue than people realize because unless you have the circ pump to keep hot water at the "leak" the whole thing cools together and you would never notice it.

Last edited by Sureshot; 09-15-2013 at 03:27 PM.
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Old 09-15-2013, 03:57 PM   #58
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Hot water from cold pipes, plumbers are stumped


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Originally Posted by Sureshot View Post
I would disconnect the cold side at each fixture, wash machine etc and see what happens. If it is at the kitchen sink that is the first place to look. Some thought needs to go into the procedure.
That was one of the first things I tried (well, actually I turned off the hot, not the cold, but surely that's equivalent). It didn't identify the problem. If you read the whole action-packed thread, you'll see that I went beyond that, and for the fixtures were I couldn't disconnect one side, e.g. in-wall shower mixer valves, I removed the face plate and checked the temperatures of all supply connections with an IR thermometer, looking for warm lines. Again, I found nothing.

Quote:
Originally Posted by Sureshot View Post
Increasing the cold pressure is not going to help IMHO because the circ pump will always be additive to the pressure. Possibly their is a pressure balance valve but I am unaware of the products available. Possibly a check valve on the cold at the offending appliance or fixture is all it will take.
I have checked every valve I'm aware of in the house, and all seem fine. I guess it's possible I have two bad valves, and thus disconnecting them one-at-a-time was insufficient to eliminate the problem.

I tried contacting my home's builder to find out if maybe there is a thermostatic mixing valve hidden somewhere in the plumbing, but apparently they view plumbing plans as proprietary information and wouldn't help me.

Quote:
Originally Posted by Sureshot View Post
Edit: I was thinking that since the wife has been gone a few days and I have been in the shop I would get a good read on my "leaks". But since we don't have the circ pump all my lines are at room temp on both sides. It may be a bigger issue or non issue than people realize because unless you have the circ pump to keep hot water at the "leak" the whole thing cools together and you would never notice it.
That's an interesting observation. I had previously found that turning off the recirculating pump made the problem disappear, and had assumed this was due to the lack of extra pressure on the hot water lines. But as you say, the leak may have been continuing as usual, but it wasn't noticed since the hot water lines had cooled down.

Quote:
Originally Posted by broox
Could it be crossing through your washing machine?
I don't think so, since the problem persisted after I turned off the hot supply line to the washing machine.

That said, I noticed from my water pressure gauge that when the washing machine starts filling, the hot water pressure drops dramatically (e.g. from 60+ to maybe 35). That was before I installed the check valve on the cold line.

Quote:
Originally Posted by markstg
So what is the purpose of the Heat Traps you had installed on water heater inlet and outlet piping? These don't work?
First, I should point out that the WH claims to have heat traps installed on both the cold inlet and hot outlet connectors, so my added heat traps should have been redundant. But the point of heat traps is to stop convective heat transfer. Hot water is lighter than cold water, so without heat traps you can get hot water rising up through your cold water pipes simply through convection. With a large two-story house like mine with the WH on the ground floor, this could result in a large amount of hot water sitting in the cold pipes.

Quote:
Originally Posted by Adamas
So the answer is to increase the incoming cold water pressure??
As Sureshot stated, that seems unlikely to make any difference since the recirc pump adds a relative pressure to the hot water, so both would increase. And I should mention that for different reasons, I did increase the cold water pressure from 60psi to 70psi many weeks ago, but it had no impact on the problem.

Quote:
Originally Posted by Adamas
Maybe the HWT is set at too high a temp warming all the surrounding piping so it doesn't matter if there is a check valve;
I don't personally find that plausible, unless my pipes were made of superconductors. But plumber #2 who tried solving my problem was just certain all my problems were due to me setting the WH too hot, so to appease him I dropped the temperature setting from above "C" to "B" for a couple days, and it made no difference except to anger everyone in my family.

Adamas had some other questions and suggestions, but most have been addressed in previous posts so I won't repeat things here. The key point to remember is that the system worked fine for 10+ years, and then started showing this problem sometime after a new water heater was installed, but without any other changes to the plumbing. So it can't be a basic structural problem that would have existed since the house was built, e.g. pipes too close, attic heat, etc.

/Seabeast
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Old 09-15-2013, 04:20 PM   #59
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Hot water from cold pipes, plumbers are stumped


What other fixtures use a single handle faucet that are within 20 feet of your kitchen? Including your kitchen faucet. Also what brand name are the single handle fixtures.
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Old 09-15-2013, 04:46 PM   #60
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What other fixtures use a single handle faucet that are within 20 feet of your kitchen? Including your kitchen faucet. Also what brand name are the single handle fixtures.
The only other nearby single-handle faucets are two Delta brand shower valves, and a Price-Pfister faucet next to the washing machine. Not sure those are all actually within 20 feet, but they're closest.

/Seabeast

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