I'm not sure how it works, but I have the same thing. What I do know is that while underway this system heats the hot water in the tank, because when we arrive at camp site after a full day on the road, Shazam! Hot water a plenty. Most times we don't even need to turn it on till next morning for shower, dishes, etc. I don't do anything more then drain the tank, shut off the fill valves (ie bypass the heater) , and then winterize with RV antifreeze (pink stuff. I fill through the water pump by means of installed bypass valve available at most RV centers. Don't forget to drain the icemaker if you have one. I have done this for four winters and have had no problems.