Getting the RV ready for winter storage and protecting it from weather-related issues
In addition, drain the fresh water storage tank and the water heater. The water heater will be equipped with a drain plug or a valve accessible from outside the RV, behind the heater door. The point, obviously, is to eliminate as much moisture as possible from the fresh water lines throughout the coach.
You can choose to simply leave the fresh water plumbing lines and all fixtures void of liquid (dry method), or employ what the RV industry calls the wet method. I recommend using the wet method if sustained below-freezing temperatures are expected. This involves the use of RV antifreeze and does not require the absolute removal of all existing water. But I must emphasize that you should use RV antifreeze approved for fresh water applications. Every season I receive a cache of emails from dismayed RVers who inadvertently used automotive antifreeze solution.
When filling the system with RV antifreeze, just add a few gallons to the empty fresh water tank and turn on the water pump. The size of your particular plumbing system will determine exactly how many gallons of antifreeze will be needed. With the water heater in the bypass mode, you won’t be adding antifreeze to it; just leave it empty and lightly thread the drain plug in place. Pump the antifreeze into the system until the colored liquid appears at every faucet and fixture. When using RV antifreeze, disconnect or bypass the water purification system (if your RV has one), as some filtering media may be damaged by the solution. It also is best to avoid purging the ice maker with RV antifreeze, as the taste may linger for a long while in the mold.
There should be enough antifreeze to cover the complete bottom of each tank. As an alternative, it is permissible to use windshield washer fluid in the gray and black holding tanks to save on the cost of RV antifreeze (check for possible local regulations against this, however). Windshield washer fluid will not harm the tanks, the drains, or the valves. To retain and protect the water seal in the P-traps, pour 1/4-cup of RV antifreeze or windshield washer fluid down each drain.
Inspect the front firewall, as well as the complete undercarriage, for openings and gaps around wiring harnesses, plumbing drains, propane tubing, etc. Seal all gaps with caulking or Eternabond tape. Any air leak can contribute to the accumulation of moisture inside the coach. Plus, sealing off such openings and gaps can eliminate the potential for critter infestation.
Aside from making sure the furnace and thermostat are turned off, it’s recommended to use tape or aluminum foil to cover the intake and exhaust vents. Blowing snow can enter the furnace through the vent assembly; melt; and cause oxidation to permeate inside the combustion chamber.