What is the purpose of an air gap in a dishwasher drain connection?

• A. To prevent siphonage back into the potable supply
• B. To filter dishwasher effluent
• C. To regulate temperature of dishwasher water
• D. To vent air from the piping

Answer: (A)

An air gap's job is to prevent siphonage back into the drinking water supply by creating a physical air break between the dishwasher drain and the home’s drain. The dishwasher drain hose goes to the air gap, which sits above the sink, and then a separate path carries the wastewater down to the drain. If pressure changes or a blockage occurs, dirty water can’t be sucked back into the potable supply because the open air space breaks the connection. It’s a backflow prevention measure, not a filter, temperature regulator, or vent.