Winterize the Drainage System
By now all the water should be cleared from the water lines. It's now time to winterize the drainage system.
There's a certain part of a drain line called a trap. The trap is located underneath the drain of each sink and is meant to constantly hold water acting as a plug to prevent sewer gases from entering the home. Go to each sink, get plumber's antifreeze and pour about a 1/2 cup down each drain.
Finally, check the water heater one last time for water, and then disconnect the compressor.
Don't neglect the tubs and showers; even though they're in the floor, they can still freeze up. Pour a small amount of plumber's antifreeze into the fixtures.