On the electric side of the water heater, besides the switch on the camper control panel, check on the water heater itself. If you open the cover on the water heater many of them have an on off switch on the lower left hand side. It is one built into the water heater as a safety precaution. If you drain the water heater without it being shut off, you will burn out the electric element immediately. Even if you've shut off the switch inside, I would recommend shutting off this switch before draining also, just to make sure.
Roger & Cheryl Full Time since 2002, RVing since 1975 2008 Chevy 3500 Crew Cab Dually, 2012 RW 36RL