Air Gap

An air gap is an unobstructed physical separation between the outlet of a potable-water supply and the flood-level rim of a receiving fixture or vessel. It is a simple, reliable method of preventing contaminated water from flowing or siphoning back into the clean water supply.

Why an air gap matters

Kitchen equipment may be connected to drains, sinks, dishwashers, ice machines and other fixtures where contaminated water can be present. If a water outlet is submerged or too close to a contaminated receiving point, backflow can occur under certain pressure conditions. A correctly designed air gap interrupts that pathway.

Examples in a commercial kitchen

• An ice machine drain discharging above a floor sink or receptor rather than being sealed into the drain line.
• A potable-water outlet positioned above the flood-level rim of a sink or tank.
• Equipment discharge arrangements designed so wastewater cannot contact or flow back into the drinking-water system.

Air gap versus other backflow protection

An air gap is a physical separation. A mechanical backflow-prevention assembly uses valves or other components to prevent reverse flow. Which protection is required depends on the equipment, hazard level and applicable plumbing code.

Chef’s tip: Never improvise an air-gap dimension. Required clearances depend on the fixture, outlet configuration and local plumbing requirements. Have installations checked against the applicable code by a qualified professional.

Key distinction: An air gap prevents a direct connection between the potable-water outlet and the receiving fixture; it is not simply an open space somewhere in a drain line.