Two separate methods of heating.....120V AC electric element and Propane
Two separate switches to turn on each one.
120V AC circuit breaker and switch on water heater are for electric element
Switch inside on panel......propane
The Circuit Breaker and outside switch off with tape over them....that is go they didn't get turned on without water in WH tank. Element burns out quickly when not submerged in water.
One at a time or both for heating water....your choice. Fastest recovery is with both on. Electric is a 1400W element....also has it's own set of 120V AC t-stats
Propane is 12,000 btu burner and has it's own set of 12V DC t-stats.
The clear tube as mentioned is for winterizing...sucking anti-freeze out of bottle and pumping thru system with rv on-board pump.
Common language Suburban WH Guide.......great info with pictures
LINKHave fun with your camper!