Your
engine coolant might take a loop through your hot
water heater, but it's unlikely to leak into the hot
water since that system is normally pressurized. But if you have a leak inside the hotwater tank it is another place to look. Are you getting any leakage into the
bilge or from the engine
water pump? The
water pump is the most likely source, usually the bearing seal goes, then the thing drips as a warning before the whole thing lets go.