If the RV has been in service all summer then it's pretty easy. Just turn all valves (one, two or three) the opposite way from how they've been all summer. You need a way of preventing water from the inlet from entering the heater. YOu need a way to allow water to go around the heater, and you need a way to prevent water from back filling the water heater through the outlet pipe. There are a number of ways to do these things that include either manually operated valves or check valves and three way valves that are "either/or" valves.
Good luck / Skip
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR - 2004 F-150 HD (Traded after 80,000 towing miles) 2007 Rockwood 8314SS 34' travel trailer
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