Remove all food from the trailer that could go bad during the winter months. Canned items should not be left in sub zero temperatures or they will perish.
Turn off the refrigerator and open all the doors on the refrigeration unit. This will stop lingering odors and prevent moisture buildup.
Ensure all the windows are properly closed and that the doors are locked. Also, make sure the roof vent is properly closed.
Check the roof for places snow or water might pool. If there are any spots you are concerned about, raise or lower the tongue jack accordingly.
Cover the tires. If you are worried about winter storage damage, keep in mind that UV rays from the sun are more damaging than covering your tires for the winter. Tire covers can be purchased from RV accessory stores, or may have been included with the purchase of your camper trailer.
Place steel wool in any areas that rodents could gain access to the trailer. Look under the trailer for small gaps between the walls and the floor. Make sure to place the steel wool in the vents and around the outside furnace vent to prevent rodents from entering.
Remove all the water from the trailer's plumbing system using compressed air to blow out the water lines. Use an air compressor and a Schrader valve to attach the air compressor to the water line of your trailer. Turn on the compressor and wait until there is no water vapor coming from any of the faucets or the showerhead. This method is called blowing out the water lines and is effective if you have time to wait until all the water has been emptied.
Pour antifreeze into the fresh water tank if you don't want to blow out the lines. Non-toxic antifreeze can be purchased at most hardware stores. Run all the faucets and the shower until the water comes out the same color as the antifreeze you added; usually this is red. Make sure you flush the toilet until it also becomes red. Finally, run some hot water to get antifreeze into the hot water tank. This is an alternative to blowing the water lines.
Dump a quantity of antifreeze into the water tank. Turn on the water pump to pump the antifreeze through the system. While this method uses less antifreeze than the method from Step 2, it is one of the less effective methods and is therefore less favorable.
