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

Cold water is hot due to amateur plumbing

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