The toilet is winterized differently than the other fixtures because of a control called a ball cock, which lets the water into the tank. Completely drain the water out of this area.
With the system completely charged, hold down the flush handle. The water will drain out of the tank, and air will start coming through the pipes, which cleans out the ball cock. Hold the handle until all the water is out of the tank, and then let it go. Finally, shut off the valve.
With the water out, it's time to add antifreeze. Wear safety glasses in case it splashes. Always use non-toxic antifreeze rated for plumbing systems. Pour it into the tank -- not the bowl. Hold down the flush handle to flush the antifreeze out into the bowl and drain the 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.