Aqua Hot, as another poster stated does NOT have a water reservoir at all. There is a small diameter copper coil running thru the Propylene Glycol tank. The propylene Glycol IS antifreeze. The CORRECT winterizing procedure is done 2 ways. First way(which I do on customers units) is to blow out the entire Fresh water system. Aqua Hot states that even blowing out, there will be water residue drops remaining in that coiled copper tube, so you then must pump RV antifreeze thru that coil. You open the Hot water drain valve(which is NOT part of the Aqua Hot) and use the on board fresh water pump to pump antifreeze until the pink comes out the Hot water drain valve. Usually less that 1.5 gallons is needed. Which is what I do. Now the Aquahot is protected from freezing. The 2nd way is to just forget blowing out and pump RV antifreeze thru the complete fresh water piping system. Doug