Be Real Careful Flipping switches before you know what they do/control!
Anything that has "W/H, Water heater" DONT Turn ON,until you are 100% sure there is WATER in the Water Heater Tank and the water supply is Constant to it! This can be City or Pump supply! Your unit should have a switch on the Tank,one one the wall for propane maybe even a switch for Elect. on the wall also,as well as a Breaker in your Main control panel for the W/H also! Until you know 100% about the Water Heater Procedure I am just trying to Save you some Headaches and $$$!
PS, this is a area "W/H" that turning on the switch at the Wrong time if Only for 2 Seconds cost $$$!