Transom Shower-hot water from both sides

[danv13]

The transom shower only flows hot water no matter which valve is opened-hot or cold. Just replaced the mixing valve behind the shower box, but that did not correct the problem.
Any thoughts?

[Black_Diamond]

did you run it long enough to flush out the hose?  My 'cold' side runs hot/warm if I have been under power awhile.  Just run the cold longer..and the hot side will be HOT so you need little hot to cold in my experience.

[alswagg]

You can add a one way valve in the cold supply line close to the water heater.  Previous post is correct by saying when you run the engine for awhile the hot enters the cold supply.   When you run the motor for a long time, the temp of the engine is 160* the water heater is regulated at 140*.  The engine can acutally raise the hot water temps past the 140* mark, which builds pressure in the tank, higher than the 40lbs the fresh water pump can produce, hence the hot water backflows into the cold system.  You can pick up a one way valve at a good hardware store, you know the mom and  pop style that has one of everything.   Al