I "winterized" our Pleasure Way Pursuit yesterday. I drained the water tank down to about 8 gal. and poured 3 gal. of RV anti freeze into the tank. Then I ran all the sink faucets both hot and cold, ...
Water heaters have bypass valves so antifreeze doesn't go in them other wise you'll need 6 gallons just for the water heater. It's a lot easier to bypass and drain the tank.