What Is an Air Gap?
An air gap is an open space that separates a water supply from a drain or other possible contamination source. The space stops dirty water from flowing backward into the clean water line. Air gaps commonly appear at sink-mounted dishwasher connections and other plumbing points that need backflow protection.
Quick Facts About Air Gap
Category
Backflow protection
Used for
Separating clean water from drain water
Common confusion
Often confused with a vacuum breaker
Also called
Air Gap Fitting
Often discussed with
Backflow Testing
Key Takeaways About Air Gap
- An air gap uses open space, not a mechanical valve.
- The separation helps protect the clean water supply.
- An air gap isn't the same as a vacuum breaker.
How Air Gap Works
An air gap works by leaving open space between a water outlet and the receiving drain or vessel. Water can fall across the space, but contaminated water can't travel backward through a solid connection. This design protects the supply line without relying on moving parts.
Related glossary terms: Backflow Preventer, Check Valve, Vacuum Breaker.
Plumbing systems use air gaps at points where backflow could reach drinking water. A dishwasher may discharge through an air gap fitting mounted beside a sink faucet. The fitting sends wastewater through a visible opening before it reaches the drain. During backflow testing, a plumber checks the setup, connections, and discharge path for signs of blockage or improper routing.
Expert Note
When we check an air gap during Backflow Testing, we inspect the physical separation and follow the discharge path. We also look for blocked openings, loose connections, or routing that could let wastewater reach the clean supply. The visible opening must stay clear so the protective gap can work.
Air Gap in Practice: A Real-World Example
A dishwasher drains through an air gap fitting beside a kitchen faucet. During Backflow Testing, we check that wastewater reaches the drain correctly and that the opening stays clear.
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Related Terms
Backflow Preventer
A Backflow Preventer is a plumbing device that keeps contaminated water from flowing backward into a…
Check Valve
A check valve is a one-way plumbing device that lets water flow forward and blocks reverse…
Vacuum Breaker
A Vacuum Breaker is a backflow prevention device that admits air into a water line when…
Siphon
A siphon is a flow path that moves liquid from a higher level to a lower…
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