DANCO 1.75 in. O.D. Kitchen Air Gap Cap in Brushed Nickel

The DANCO Air Cap prevents sewage from flowing back into the dishwasher. When water flows through the drain hose, it creates a suction on the water still in the dishwasher. The air gap, makes a hole for air to get in. That way, the water only leaves the dishwasher when it supposed to, when it is pumped out.