Do I need an air gap for the drain hose?

You must use an air gap if the drain hose is connected to house plumbing lower than 20 inches (50.8 cm) above the subfloor or floor. Check local codes to determine whether an air gap is required in your area. When connecting the air gap, a rubber hose (not provided) will be needed to connect to the waste tee or disposer inlet. (Page 6)