To winterize an RV to prevent damage from freezing, drain the water lines and tanks and run antifreeze through all the plumbing. Any RV kept in a location that has a chance of falling below freezing in the wintertime requires winterizing.
Winterizing an RV's water system requires several gallons of non-toxic antifreeze, along with tubing and a water pump. Before beginning, study the instructions in the RV's user manual for the winterizing process for the specific vehicle. Begin by draining, flushing and cleaning all tanks and plumbing. Use an air compressor to blow out the water lines. Next, close all the faucets, and cap all drains. With the tubing, pump the antifreeze into the RV's plumbing system. Flush the toilet until antifreeze appears. Finally, disconnect the pump, and pour a cup of antifreeze down each drain.
After taking care of the water system, make sure that all perishable items are removed, as well as everything valuable and anything that could be damaged by cold, and that all power and switches are set to off. Cover any holes, vents or other gaps to prevent animals from entering and nesting inside. Put the RV on blocks to take pressure off the tires, and cover the entire vehicle with a cover made of a breathable material to prevent moisture build-up causing mold and mildew.