Patty, I have a well, water softener and electric water heater. If the water softener is off, the water with it's rust/calcium etc, goes into the water heater and the element inside collects and cooks the water residues and it smells bad.
Also, if water sits in the water heater for many days, it will get an off smell.
Do you smell it in cold water alone, or in hot water alone? Both?
Running fresh water through the system (and until the water heater has all new water in it) should make it smell better.
Once a year we also drain the water heater completely (turn off the power to it--or you'll burn out the elements) and flush it with clean water and then fill it up again (THEN turn on the power again).
Let us know......