My hot and cold water pipes appear to intersect at some point

[Casecapital]

Hello,

I'm replacing our water heater.

STRANGE - before I removed the old water heater, I touched the two flex hoses attached to the top of the water heater. There was a copper pipe that came out of the left side of the wall (that did not have a shut-off valve attached to it, until I put one on)....and this one was attached to the top left of the water heater (which said "HOT" next to this nipple). However, when I touched it, it was cold.

And the copper pipe that comes out of the right side of the wall (that did have a shut-off valve attached to it by the plumber that replumbed our house when we renovated 10 years ago)...and this one was attached to the top right nipple on the water heater (and it said "COLD" next to this nipple). But when I touched this one, it was definitely hot.

So, it is like the plumber did everything in reverse. It is like he planned on having the copper pipe on the right Side be the cold intake, (that comes from the street) and that is why he put the shut-off valve on that one and attached it to the top water heater that said "COLD" next to it.

However, as I said, when I touched that one, it was hot to the touch, and the left one was cold.

I didn't think too much about it (other than he hooked up the gas water heater in reverse). But then when I put the new electric water heater in, I can't get anything but warm water at best to come out of the warm taps in my sinks/tubs.

So then, I drained everything and decided to "Test" which of the 2 copper pipes coming out of the wall is the "true" cold water line coming from the street.
And here is what happened:


FIRST - I disconnected the cold intake and hot out-take.

I got to the point where I had both the cold in and hot out disconnected, and a new valve on the cold intake (so I can turn it off and restore at least cold water to the house).

But here's my huge problem:

If I leave the cold water intake valve open and turn on the water to the house again, cold water comes pouring out of the cold intake pipe as you'd expect.

If I then close the cold water intake, water then starts coming out of my hot water out take!?

It appears that my cold water line and my hot water line in my house are linked or intersect somehow? I know that when we renovated the house, they had to move our water heater from the left side of our house to the right side of our house and put it in the garage. And I do remember the contractor saying something about the plumber having to "reverse" the plumbing to get it to work correctly, but I had to idea what he meant. That was 10 years ago, and we have always had hot water, until the water heater died of age recently.

Do you think that my main cold water line, that come from the city street and feeds my house, is somehow attached or linked to the hot water line, so that they "mix"?

Any thoughts would be greatly appreciated!!

Thank you!!!

 

[Themp]

Check this page for crossover: https://www.home-water-heater.com/plumbing-crossover.html

 

[Sponsor]

 

[Casecapital]

Thank you! I will read that crossover link and let you know what I find. I truly appreciate the quick response?
Just wondering - When they moved my water heater from left side of the house to the right during the renovation, it was towards the end of the renovation, and the house had already been completely re-plumbed with the water heater on the left side. The inspector did not like it there, and made them move it to the other side of the house and in the garage. My fear is that they some how 'Jerry-rigged' the plumbing to accommodate this last minute move of the water heater, and somehow my hot water line is connected to the cold/main water line that comes in from the street.

Have you ever heard of this happening in your experience?

 

[John Gayewski]

Go around and shut off all of the supply stops on every fixture. Then do your test again. That will tell you if the piping is crossed somewhere.

Do you have a recirculation system?

Thank you! I will read that crossover link and let you know what I find. I truly appreciate the quick response?
Just wondering - When they moved my water heater from left side of the house to the right during the renovation, it was towards the end of the renovation, and the house had already been completely re-plumbed with the water heater on the left side. The inspector did not like it there, and made them move it to the other side of the house and in the garage. My fear is that they some how 'Jerry-rigged' the plumbing to accommodate this last minute move of the water heater, and somehow my hot water line is connected to the cold/main water line that comes in from the street.

Have you ever heard of this happening in your experience?

 

[Themp]

A cross over can happen in a shower valve cartridge and you usually do not have a way to turn off the supply to that valve. So, if your test for all the supply stops turned off still shows a crossover, then I would start looking at replacing the shower cartridge. If you have multiple showers, then it makes it harder to isolate.

 

[Reach4]

Troubleshooting idea. Turn off the WH. Turn off the water supply to the WH. Open the drain on the WH after hooking up a hose to direct the water where you want..

Go around to shower valved and sink valves, and feel and listen for flow. Maybe enlist the help of somebody with really good hearing. Maybe a child.

 

[Themp]

Eatherton method. The Eatherton method, which is properly named after Mark Eatherton, the
plumbing engineer who created this particular procedure, consists of testing each fixture
individually, beginning with the shower valve in the housing unit that is experiencing hot water
issues. The faceplate of the shower valve is removed, leaving the shower’s mixing valve
exposed. The hot side of the shower valve is heated by turning on hot water until the user gets
the hottest water and then turning the shower valve back off. A nearby lavatory hot water faucet
is then turned on, while the user feels the hot side of the exposed shower’s mixing valve. If there
is crossover, the shower mixing valve will rapidly cool down because the lavatory is pulling cold
water through the shower mixing valve, thus rapidly cooling down the hot side of the shower
mixing valve. If no crossover exists, the shower mixing valve will remain hot, because cold
water is not crossing over, and thus the shower valve will remain heated.

 

[Plumber69]

By chance do you have a shower or tub valve that currently has no cartridge in it? Just the test cap

 

[Casecapital]

Thank you for all of your ideas! I will begin to test my shower valves today. I have 3 to test. We didn't experience any issues or "crossover" with our old showers or faucet, but the strange thing is that when I was unhooking the old water heater, I noticed that the cold water supply line (coming out of the wall) was very warm, and the Hot water outlet pipe was cold. I have to believe that hot water from our old water heater was getting sucked back up the cold water inlet line. However, as I said, we were NOT experiencing any hot or cold water issues with our 3 shower valves or any of the sink valves. Very strange. I do not know where that hot water was going.
I will try the Eatherton method and see if I can find a valve that is bad, and post what I find out.
Thank you again for all of your ideas!

 

[Casecapital]

NEW QUESTION - Ok, I didn't seem to find any shower or sink valves that are doing any crossover, so I tried this:

I unhooked the water heater water lines - I then turned off the main water source and drained both the hot and cold water lines where they come out of the walls at the water heater area.
I have shut off valves on both the cold and hot water lines at this point, where they come out of the walls and connect to the water heater.
So, I left both shut-off valves open, and then CLOSED all of the faucets/shower vavles. I then turned the main water source back on. As expected, the water began flowing out strongly through the cold water line.
I then turned off the main source, and then closed the shut-off valve for the cold water line. I then turned the main water source back on, and expected nothing to come out of either line (since the cold line was now shut off, and the hot water line should not be connected to the cold/main water source.
HOWEVER - after about 40-60 seconds, the cold water began flowing out of the HOT water line (that would normally be the line that the hot water would flow from the water heater into the hot water lines of the house). And further, the cold water was flowing out of this hot water line about as strongly as it was previously flowing out of the cold side.

So - I have to assume that when both the hot and cold shut-off valves are open, the cold water comes from the main and naturally flows out the cold water side. However, when I shut off the cold water side, the water then backs up on the cold side, but then is somewhere "linked" or "intersects" the hot water line, and consequently fills up the hot water line and eventually flows out of the hot water line at the water heater area.

Could my contractor (during a house addition put on years ago), somehow connect the hot and cold water lines at some point in the house?

One other point - my kitchen faucet has very warm water coming out of the cold side. It is a single handle faucet, but I don't think it is crossing over at this faucet, as the angle stop feels very warm on the cold side, when it is turned on. So, that makes me think that the water coming into the "cold line" of this faucet is already warmed up somehow.

I am wondering how I determine how the cold water (that is coming from the street/main line) somehow can come out of the "hot water" line at the water heater attachment.

Thank you!

 

[wwhitney]

I have not closely followed the earliest posts, but your latest test proves you have an undesired cross connection somewhere. My first thoughts on finding it:

Locate all valves on hot and cold lines everywhere in the house, including any stops at the shower valves (behind the trim), and any fixture stops. Turn them all off, disconnect the water heater hot side connection, and open the hot water stop at the water heater. Then turn on water to the house.

If you get water coming out the hot at the water heater again, then it's much more difficult to find the cross connection. The shower valves are still a likely suspect, unless they all had stops that you were able to shut off. Any sort of recirculation is obviously a suspect, unless it is isolated by closed valves. Beyond that, some further thought would be required on how to proceed. It might require mapping out all the water piping and cutting in a few more valves to subdivide the piping.

If you don't get water coming out the hot at the water heater, then good. You can now proceed with a strategy of opening valves until you find the minimum combination of open valves that causes water to come out of the hot water side of the water heater connection. That should let you trace the piping through those valves and narrow down where you need to look for the cross connection.

Cheers, Wayne

 

[Casecapital]

Thank you for all of this information Wayne! I will try that this weekend and see if I can locate where the crossover is happening. We do have one faucet now in one of our bathrooms that is not getting any hot water on the hot side, so maybe that is the culprit?

Do you feel that there is any possibility that the plumber connected the two lines anywhere, and that we just didn't know all these years because we never changed out the water heater (and maybe the water pressure was holding the water in each line properly)?

It just seems so strange that we had not issues, until we changed out to a new water heater about 8 days ago. Seems like quite a coincidence that a shower/faucet valve would fail at the same exact time that we install a new water heater.

As I stated in my earlier post, I do remember my contractor stating that the plumber "did a good job by reversing everything", once we had to move the water heater from the left side of our house, to our right side. This change happened right at the end of the renovartion - so the house was already plumbed to have the water heater on the left side of the house. Then the inspector made them move it to the right side of the house, and I know the plumber did not want to re-plumb everything, so I feel he did some sort of "jerry-rig" to get it to work with the water heater on the right side of the house, with a minimum of re-plumbing on his part.

Any thoughts are greatly appreciated!

Thanks!
Chris

 

[Jeff H Young]

all water heaters take cold on right. sounds like crossover through a single handle handle lav , or other faucet or a tub or shower valve single handle . I cant belive youve got a cold and hotline connected for 10 years and never noticed it .
maybe on a the recent water heater install debris of some sort gets into valve or faucet causing cross over. nothing at all to do with having an electric or gas heater

 

[John Gayewski]

I'm also gonna doubt the plumber connected thr hot and cold somewhere. It kind of makes no sense.

 

[Themp]

What brand of shower valves do you have? If it is a common valve and the cartridge is reasonably priced, then you could buy three and replace them all at this point. Or if it is a brand that has a test cap that can be put in in place of the valve, then you could get a test cap(not sure they sell them) and pull the valve and replace with the test cap and re-test.

https://www.deltafaucet.com/bathroom/product/R10000-UNBX.html

Look in the description, it comes with a "Heat-resistant pressure test cap allows for air or water testing before valve cartridge is installed"

 

[NashvillePlumber]

Hello,

I'm replacing our water heater.

STRANGE - before I removed the old water heater, I touched the two flex hoses attached to the top of the water heater. There was a copper pipe that came out of the left side of the wall (that did not have a shut-off valve attached to it, until I put one on)....and this one was attached to the top left of the water heater (which said "HOT" next to this nipple). However, when I touched it, it was cold.

And the copper pipe that comes out of the right side of the wall (that did have a shut-off valve attached to it by the plumber that replumbed our house when we renovated 10 years ago)...and this one was attached to the top right nipple on the water heater (and it said "COLD" next to this nipple). But when I touched this one, it was definitely hot.

So, it is like the plumber did everything in reverse. It is like he planned on having the copper pipe on the right Side be the cold intake, (that comes from the street) and that is why he put the shut-off valve on that one and attached it to the top water heater that said "COLD" next to it.

However, as I said, when I touched that one, it was hot to the touch, and the left one was cold.

I didn't think too much about it (other than he hooked up the gas water heater in reverse). But then when I put the new electric water heater in, I can't get anything but warm water at best to come out of the warm taps in my sinks/tubs.

So then, I drained everything and decided to "Test" which of the 2 copper pipes coming out of the wall is the "true" cold water line coming from the street.
And here is what happened:


FIRST - I disconnected the cold intake and hot out-take.

I got to the point where I had both the cold in and hot out disconnected, and a new valve on the cold intake (so I can turn it off and restore at least cold water to the house).

But here's my huge problem:

If I leave the cold water intake valve open and turn on the water to the house again, cold water comes pouring out of the cold intake pipe as you'd expect.

If I then close the cold water intake, water then starts coming out of my hot water out take!?

It appears that my cold water line and my hot water line in my house are linked or intersect somehow? I know that when we renovated the house, they had to move our water heater from the left side of our house to the right side of our house and put it in the garage. And I do remember the contractor saying something about the plumber having to "reverse" the plumbing to get it to work correctly, but I had to idea what he meant. That was 10 years ago, and we have always had hot water, until the water heater died of age recently.

Do you think that my main cold water line, that come from the city street and feeds my house, is somehow attached or linked to the hot water line, so that they "mix"?

Any thoughts would be greatly appreciated!!

Thank you!!!

 

[NashvillePlumber]

You didn’t mention why changing Htr but you check hot n cold issues while all lines and water htr connected . 1st Turn off supply to Htr go around each fixture make sure you have cold on right and nothing on left. If you just noticed something peculiar while changing water htr and all was well before don’t overthink it !

 

[Casecapital]

I'm also gonna doubt the plumber connected thr hot and cold somewhere. It kind of makes no sense.

Ok, thanks! I was hoping that is the case.

 

[Casecapital]

You didn’t mention why changing Htr but you check hot n cold issues while all lines and water htr connected . 1st Turn off supply to Htr go around each fixture make sure you have cold on right and nothing on left. If you just noticed something peculiar while changing water htr and all was well before don’t overthink it !

Sorry - I replaced the heater, due to it being 20 years old and beginning to not heat properly. I put in a new hybrid electric one by Rheem. I have tested the water coming out of the new heater and it is heated to the correct temp, so I know that it is working as it should. I will try your trick tonight. Thanks!

 

[Casecapital]

all water heaters take cold on right. sounds like crossover through a single handle handle lav , or other faucet or a tub or shower valve single handle . I cant belive youve got a cold and hotline connected for 10 years and never noticed it .
maybe on a the recent water heater install debris of some sort gets into valve or faucet causing cross over. nothing at all to do with having an electric or gas heater

Thank you for this info. I have 3 shower valves and 2 single handle faucets. I have begun to order new cartridges for all 5 of these and will replace all once I have them to see if that fixes the issue. After reading everyone's responses, I have to believe it must be one of these 5 that is causing the cross-over. I will post what I find out. Thanks again!