Hello. I'm having a problem with hot water coming out of my cold water taps at times (even ones that have two handles). From what I've read, single handle faucets and valves that have become defective can cause this. Sometimes, once it starts, the hot water doesn't finally cool down after I let it run for a while. Other times, it'll cool down after a while. I'm not talking warm but hot water. I have a hot water heater and two showers with single handle valves (one is a moen) and I have a single handle Kohler forte faucet with one of those heads you can pull away from the unit. Since my Moen shower valve was leaking anyways I had my plumber replace the cartridge and now it no longer leaks. He felt inside the pipe where the cartridge goes into before he put it in to see if he could feel any grooves (which would allow water to pass he said) but said it felt ok. The new valve he put in was plastic. However, my crossover troubles still continue. I just got done turning on the kohler kitchen faucet and the water was coming out the tap was hot so i reached under the sink and felt the hot water line but it was cool, and the cold water line was hot. So it seems to me that the hot water wasn't coming from the hot water side of the kohler unit but from the cold water line itself. This leads me to believe that the odds are against there being a problem with the kohler faucet. However, that still leaves one other shower single handle valve (which I took a photo of and my local plumber supply store said was plastic and which they claim wouldn't be a cause of crossover since it was plastic). Is there any other trouble shooting anyone can recommend or any way that I can check the other shower valve (which is enclosed so i can't feel the hot and cold water lines. Also, I felt both lines feeding into my hot water heater and while the hot water line out was warm the cold water line in was also warm. Is it possible that the hot water may be coming back out of the hot water heater and going into my cold water line? Also, I have a clothes washer with a hot and cold line but it has two valves, one for the hot water and one for the cold water so it didn't seem possible to me that crossover could be happening there? Any suggestions would be much appreciated. Thank you.