I have been experiencing a problem only in the last year or two with hot water coming out of the cold water faucet when prior to this time, it was not happening. When I turn on the cold water it immediately runs warm, then within a minute it turns real hot and runs that way for about 3 minutes before turning cold again. This happens whether it's summer or winter in the Chicago area. The hot faucet starts out warm and then turns hot and stay hot which is normal. When I touch the cold water inlet on the water heater, it's a little warm but not hot to the touch. Nothing in the entire pluming system has changed during this time (no additions, changes, remodeling, etc.) so can't understand why it wasn't happening prior to 2 years ago. This happens whether it's the closest or the most remote faucet from the water heater. The problem occurs whether it's a mixing faucet valve (single handle) or double handle faucet.
The furthest mixing shower faucet is a non-scalding type where you're not supposed to get a blast of hot water if someone uses the cold water in another part of the house but that feature stopped working about 9 years ago probably due to some sediment/calcium in the valve. Just thought I'd mention that but don't think it has anything to do with the original problem.
I have a 50 gallon gas heater that is probably 11.5 years old and I used to drain it once or twice a year as recommended to reduce the sediment but I stopped doing that about 8 years ago. The pressure release valve on the heater works fine. There is no expansion tank or anything like that in my system.
Can anyone figure this one out?