Originally Posted by Bill M.
The heater is not original if it has the styrofoam insulation. ...... If you look in your bathroom and there are 2 switches in a little panel for the WH then you have the gas-electric unit. One switch has a picture of a gas flame and the other has a picture of an electric bolt.
There are also some add on electric elements for a gas only WH. Look to see if it has a drain plug or if there is a heating element with a wire to it going into where the drain plug was. My trailer had a rig like that on it when I bought it. Not a very good system in my opinion.
I agree styrofoam = replacement, but the switch may not have been installed as described.
Is there a plate with WH make and model?