: I never heard of this problem before. : If its a gas heater, I might check to make sure the burner is working normally. It could be burning poorly and causing a smell. Or the flue could be clogged. : If an electric heater, I would smell around the electrical connections to see if one of them is burning from a poor connection. : If this doesnt help, repost your question and say what it smells like and when. : Rotten egg smell from the water is commom.Rotten egg smell is indicative of hydrogen sulfide present in the hot water from the reduction of naturally occurring sulfates in the water source. I suspect anode failure in the water heater is causing this phenomenon. If so, replacement of the anode is indicated. It can just be removed without replaceemnt, but this will decrease the life of the heater.