I have a 2012 31SB Zinger that has a Atwood hot water heater. It came with a plastic plug, and according to the documentation, it does not take an anode rod. I am assuming it's an aluminum tank. I have been using the plastic plug it came with and had no problems, but can some other owners confirm this? I drain the water heater after every use, and flush it. Also, does anybody know where the by-pass valve is for winterizing this? I like to bypass the WH when I do my antifreeze, and I am sure it's in there.