Cold water on hot side

[Victory Magnum]

Hello, i am hoping someone can help. My heating and plumbing has worked fine since i built my house 10 years ago. Then i started getting very hot water when i turned my cold faucets on. I had my honeywell am-1 mixing valve replaced and it is still doing it. I have a Biassi boiler and an indirect water heater. All my faucets have separate direct lines off a hot and cold manifold respectively. The cold supply feeds my indirect water heater at the bottom and also supplies the cold manifold from the cold water storage pressure tank. The mixing valve was set up with the cold side facingmthe cold manifold, the hot side facing my hot manifold and the mix port is fed from the top ofmthe indirect heater. My thought was there should be a check valve to stop the hot water from flowing to the cold manifold and that once the water mixes it would only be allowed to flow to the hot manifold. Am i kissing something. I cant find a diwgram online that looks like mine. The odd part is that it also worked flawlessly for 10 years. I can add a pic if necessary. Thanks

 

[Jadnashua]

Some single-handle faucet designs, when they start to fail, can allow the hot/cold water to cross over. That is a much more likely candidate as the source of your problem, especially after replacing the tempering valve and getting the same results.

 

[Sponsor]

 

[Victory Magnum]

Some single-handle faucet designs, when they start to fail, can allow the hot/cold water to cross over. That is a much more likely candidate as the source of your problem, especially after replacing the tempering valve and getting the same results.

I can feel the hot water in the cold manifold. It is every faucet

 

[Reach4]

I can feel the hot water in the cold manifold. It is every faucet

Don't use hot for a while, so the hot pipes cool. Run cold that turns hot from one of your fixtures. Feel the pipes out of the hot manifold several feet from the manifold (do your best given the access). The hot one is the one connected to the fixture doing the cross-connect.

If this does not work, and your manifold has individual valves, close half of the valves. Does the problem happen? Try the other half closed. You can do a binary search, and locate the culprit pretty fast I am thinking.

 

[Jadnashua]

Do you have a hot water recirculation system?

 

[Victory Magnum]

Here are a couple photos

 

[Victory Magnum]

 

[Victory Magnum]

The top photo shows cold manifold on left, hot on right and mix valve in the middle. I would think that the water could not flow thru the mix valve into the cold but rather feed the mix valve thru the cold. If I run the cold a while it will get cold and then the manifold is cold. As soon as I turn it off the hot water flows right back into the cold manifold and it is hot to touch.