Pour about a cupful of antifreeze into every drain to displace the water and protect the trap.

Finally, dump the holding tanks and pour a pint or so of antifreeze directly through the toilet and the tub drain ...

... to protect the dump valves.

Winterizing the ice maker

This is cut & pasted from the Dometic manual ...

Follow these Steps:
• 1. Shut off water supply valve to ice maker.
• 2. Place a shallow pan under water solenoid valve.
• 3. Remove inlet fitting to ice maker water solenoid valve. Drain water from the supply line.
• 4. Remove the plastic nut and water line from outlet side of water solenoid valve. Drain water from the line.
• 5. Cycle ice maker several times while blowing compressed air through water solenoid valve. Be sure all water is out of the solenoid. NOTE: Up to 40 PSIG air pressure can be used to clear the valve.
• 6. Reconnect and tighten lines on water solenoid valve. Leave the water supply turned off until temperatures are above 32°F/0°C.
• 7. Dry out ice maker mold assembly with soft cloth. Place bail arm in UP/OFF position.

Winterizing the washer/dryer combo:

• Set the water temperature control to warm - this will fill both the cold and the hot lines with antifreeze.
• Turn on the unit and run about a gallon of antifreeze into the unit.
• Turn the control to spin - this will allow the pump to run the antifreeze through itself and then through the drain hose.
• Pour a cup down the drain to be sure that the "p" trap is filled with antifreeze.