[rohrmann]

The real reason for the outside switch is to protect the electric element from someone turning on the electric without water in the tank. The original switches also came with a small cotter pin which kept the switch in the off position. When winterizing, it is advised to turn the switch off, just in case someone forgets to fill the water heater with water before turning on the electric after de-winterizing, of course no one would ever forget to fill the WH tank.