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.
