The air gap body separates the hose running dirty water from the hose running to the drain. It is a simple way to make certain wastewater and debris never re-enter your clean water supply.The dishwasher air gap is mounted above the sink and prevents contaminated water from re-entering the dishwasher from the drain via backflow. Since these two paths never intersect, there is no risk of wastewater creeping back into your clean appliance.