Dishwasher high loop is always needed

Discharge, Loop and Air Gap

The dishwasher discharge hose should be connected to the waste tee or disposer inlet above the drain trap. It is recommended that the drain hose either be looped up and securely fastened to the underside of the counter, or be connected to an air gap.

Dishwasher must be connected to waste line with a 32-inch minimum high drain loop or an air gap above the counter top surface, depending on local codes, to prevent back flow and contamination into the dishwasher. An air gap must be used if the waste tee or disposer connection is less than 18 inches above the floor to prevent siphoning.