A dishwasher air gap is a fitting mounted about two inches above the sink that prevents contaminated water from re-entering the dishwasher from the drain via backflow. An air gap is a simple way to ensure wastewater and contaminants never re-enter your clean water supply.

The dishwasher air gap is a chrome or stainless steel cylinder fitting that can be found at the back of the sink near the faucet. Under the countertop, you’ll find two branches of hose which allow the air gap to connect your dishwasher to the sink drain, preventing dirty water from coming in contact with your clean dishes.