I was in the process of performing minor repairs on my tankless water heater when I realized that I was unable to fully stop the flow of water out of the hot side of my faucets. I then realized that it was cold water flowing from the hot side. The flow is steady and about 1/4 to 3/8 inch in diameter. I have numerous single handle faucets in my house. I have been told that they are a likely source for this problem. I was also told that by turning on the hot side of one of my two handle faucets and then in turn moving each of the single handle faucets to the cold side that the water would stop flowing from the two handle faucet when the faulty single handle was turned to cold. I tried that but with every single handle faucet turned to cold the cold water continued to flow from the hot side of the two handle faucet. I am not sure what to try next or what else could be the problem. Someone else suggested you could feel the hot lines under each sink and the one that get cold is the faulty sink but I an not sure how to test that.

Thanks

To check by feel, go to one sink, run hot water until it is hot. Shut it off. Go to another sink, and leave the hot on. Go back to the first sink, reach under the sink and feel the hot water pipe. If it cools far faster than you think it would, likely that is the bad one.

Another think you could try is shut off the hot stops. Most sinks and tubs have valves under them you can shut the water off to the faucets. Then any faucet where you can get cold water when turned to the hot, likely is the bad one. Note, if you get hot water, the hot stop is bad.