Originally Posted by aspects
its not necessary. only if the waterlevel goes below the heater
Agreed! As long as heater is under water, no need for unplugging. IMO, constant plugging and unplugging may shorten its life. I usually placed it horizontally so that heat can be distributed better in the tank. The way heater is built is that thermostat is right above the heating elements. Thus when placed vetically,heat rising can affect the thermostat before heat is properly distributed (constant on/off).
When horizontally positioned, heat from elements will rise w/o affecting thermostat too much thus heat is properly distributed.