Cold water is hot due to amateur plumbing

steam-rookie · May 3

the hot water tank in the photo is being used for storage only. The coil in the boiler still works, and produces plenty of hot water. All of a sudden, out of nowhere, the cold water is mixing with the hot water. I am getting hot water from all of the cold water taps

IMG_1647.jpeg

IMG_1648.jpeg

in the house.The current set up has been like that for many years. I have been told on numerous occasions that the pump is in the wrong place. I have been told it should be on the top somewhere.
so, looking at the photos. Can anyone tell what is wrong and why I am getting mixing with the Hot Water into the cold taps.

EdTheHeaterMan · May 3

Check valve missing

Screenshot 2025-05-03 at 10.38.44 AM.png

neilc · May 3

~~is the recirc running?~~

~~does it have a check?~~

~~and or is it stuck open?~~

yeah, nevermind, still need a check on the cold supply to the domestic hot

Mad Dog_2 · May 3

You have a cross-connection somewhere. The usual suspects...

Single handle mixing valves like shower bodies, Washing Machine valves.
Mop Sink connections that are altered.
Domestic hot water coils using a globe valve to blend.

Yes, you also may need a check valve, but when this condition "suddenly" occurs, it's usually at the aforementioned locations. Mad Dog

EBEBRATT-Ed · May 3

Agree with @Mad Dog_2 if the problem just started a check valve may not be the fix.

steam-rookie · May 3

thank you for the quick reply.

There used to be a check valve just after the pump where the red valve is located. It caused a lot of water hammer when the washer went on, so I took it off. The only other thing that has changed that I think of is that the heat is off. Anyway, I think installing a check valve at the new suggested location looks like something I could try. I like that idea because it’s way closer to where it seems like it’s mixing to me.
that pipe coming down should be ice cold. It’s pretty much hot all the way up now. Maybe placing the check valve there might be a really good idea.

hopefully when we run the washing machine there won’t be a lot of banging

neilc · May 3

if you innstall the check on the feed to the DHW, you might / will need an expansion tank on the hot side since the DHW will be isolated from expanding back to the house side,

and what Ed Mad Dog says, Cross Connections ?

mattmia2 · May 3

https://forum.heatinghelp.com/discussion/comment/1854412#Comment_1854412

I was about to say that then looked at it more closely and i think the check is just on the bypass, the dhw system is still open to the cold water inlet through the coil.

steam-rookie · May 3

I believe that the last comment made is correct.
The check valve should be on that cold water inlet.

if it starts to have water hammer I also agree about the expansion tank. There has never been an expansion tank anywhere

That will be my next question without a doubt.

Larry Weingarten · May 3

Hi, If you put a check inline before the water heater, thermal expansion will have no place to go, so will raise pressure until the relief valve lets go. So, an expansion tank is needed if a check is put upstream of the water heater.

I'll add that the test for cross connection is pretty easy. Just turn off the cold supply to the heater and open a hot tap. Water should stop flowing in seconds. If it keeps running, you get to hunt down that cross over. 🤠

Yours, Larry

EdTheHeaterMan · May 4

I also agree that using the check valve will require an expansion tank like this one: https://www.supplyhouse.com/Amtrol-140N43-THERM-X-TROL-ST-5-Expansion-Tank-3714000-p

steam-rookie · 8:23PM

thank you for the replies.
this plumbing set up has been running without any issues for over 30 years

Nothing has been changed. This problem seems to have coincided with the thermostat, no longer calling for heat in the house. The weather has gotten warmer in New York.

I felt the cold pipe leading into the boiler. It was hot. As a matter of fact, I continued upstream and still hot. I followed the pipe around the basement and everywhere it should’ve been cold it was hot. It finally felt cold Just before the meter where it comes in from the street.
One thing I did notice is the pump seems to be running much more than usual. During the winter, it hardly turned on at all. But now, every time I go down into the basement that pump is on.
so, instead of pumping the water into the coil. It seems to be pumping the water back up into the cold supply.

Maybe the coil got clogged up. I don’t know. About the cross connection discussion. I don’t think a cross connection is possible because I haven’t done anything to the plumbing. Please let me know if I’m wrong about that. Do cross connections just happen on their own.

here is some more info.
The hot water in this house comes from the coil in the boiler. The pump pushes water from the tank into the coil and then back out from the coil into the tank. There is nothing heating up in the hot water heater. It is a storage tank only.

The system has three thermostats.
There is one on the boiler. And there is two in the hot water tank. They are all active. The thermostats top and bottom in the hot water tank turn on the pump.
like I mentioned before, this system has been working very well for many years.

Sometimes, I could feel the hot water creeping up that cold supply pipe. But would only get about a hands length and then the pipe would be cold again.
In other words, there has always been some mixing without the check valve. But it has been extremely minimal. Maybe 6 inches or so up the pipe. currently that 6 inches has turned into the entire cold water supply all the way to where it comes in from the street.

This situation, to say the least, has been very alarming. And, I don’t know what to do about it. Frustrating.

The only other thought that I have is this:

is it possible that because the boiler is not turning on as often as it did in the winter. Would it be possible that the thermostats in the tank are set to high thus causing the pump to stay on much longer than it used to

I did not explain that well, but I have a feeling that the thermostats in the tank are not in alignment with the thermostat on the boiler.
That would explain why the pump is constantly running. And maybe explain why the hot water is backing up into the cold water system. it’s possible that the coil maybe can’t handle the pump being on for that long.

Does this sound reasonable to anyone.

steam-rookie · 8:26PM

I have another question.

is it even possible that the little pump could overcome the water pressure that comes in from the street.

Cold water is hot due to amateur plumbing

Comments

Categories