I copied this from an earlier post:
How to Winterize Your ParkLiner
A Step-by-Step Procedure
For those of you who have decided to park your ParkLiner
for the winter, there are some easy steps you should take to ensure your unit is securely winterized, so it’s ready to roll with no issues in the spring. Follow these, and your ParkLiner
will weather the winter like a breeze.
1.) Thoroughly clean your ParkLiner, and remove all food and fragrance-bearing items.
2.) Shut off your water pump if it’s on.
3.) Open the *drain valve on the **fresh water tank (located on the bottom rear-facing side of the port side tank).
4.) Open the drain valves on water system’s pressure side (located between the starboard (curb) side wheel well and the hot water heater, as viewed from the inside of the trailer). You will have to reach down to access them.
5.) Open the faucets in the bath and sink, and flush the toilet if so equipped.
6.) Remove the anode rod from the water heater as per the manufacturer’s instructions. A ratcheting socket driver works best (1 1/16-inch).
7.) Walk around the trailer and look to make sure the system’s water has finished draining before proceeding to the next steps.
8.) Close the fresh water tank *drain valve (the one you opened in step No. 3).
9.) Close the cold water pressure *side valve (located on the white pipe that opened in step No. 4).
10.) Close the water heater *bypass valve (located between the water heater and the cabin face of the rear bench just to the right of the galley).
11.) Close the faucets in the bath and galley.
12.) With the help of a funnel, pour one gallon of RV antifreeze into the fresh water tank; some systems may require more.
13.) Turn the water pump on.
14.) Open the cold water faucet in the galley until antifreeze runs out; then close it.
15.) Flush the toilet until antifreeze runs in to the bowl; then flush it a few more times.
16.) Open the cold water side of the shower faucet, and turn on the shower pump; make sure antifreeze goes down the shower drain.
17.) You are done until spring!
*The drain valves are high quality brass ball valves. They are opened and closed by moving a lever 90 degrees. When the lever is parallel to the pipe, the valve is open, and when perpendicular, it is closed. Campers with an outside faucet may not have a cold water pressure side valve inside; drainage is via the outside faucet.