Can't help with manual by in most RV's there is a low point drain for water System. open it and all water tank valves . As to the Hot water heater there will be a drain port at the outside door( there maybe inside or outside a bypass valve/valves to bypass the tank. Then either blow air into the system and clear all water from faucets. Then the pink RV anti freeze in the traps. a little in the shower and a little in the toilet. A popup is very EZ to follow pipes and see what is needed if you can't find a manual. The Refer, I think that is what your asking, is just shut off and leave open so no moisture causes mold or bad odor. For winter storage a small Elec heater or a couple light bulbs help keep the RV nice and dry.