I have been experiencing problems in one of my bathrooms. When the shower is first turned on it is hot, within 30 seconds it gets cold. I have hot water mixing with cold water in the toilet, and hot water mixing with cold water in the cold water side of the sink. When I shut off the hot water supply to the bathroom, I get cold water coming out of the hot side of the sink. There has been nothing changed in the bathroom within the last five years. Only changes recently has been a new furnace (1 1/2 years ago,coil hot water heat)and new water meter installed by Water Division.