Many campers have electrical elements inside the water heaters. This allows them to heat water without using LP. Many times, companies do not install an inside switch for turning the element ON and OFF. The little switch on the water heater is almost impossible to find (the first time) and almost as hard to get to so that it can be switched on and off. It also requires that you go outside to accomplish this task.
This simple mod basically cuts the hot/black 110VAC wire that runs to the water heater and splices in a new wire that feeds a switch mounted inside the sink cabinet. This allows the water heater electric element to be switched ON or OFF from inside the camper.
The outside connections need to be placed inside an appropriate electrical junction box. This video does not show that. But, I will eventually add this box just for my peace of mind! ...It's a safety thing!
Electricity KILLS. If you are not familiar with electrical wiring PLEASE do not attempt this yourself. Hire an electrician!
https://youtu.be/aO97Qm58rJQ