Which statement best defines air gap separation in a piping system?

• A. A temporary seal that prevents backflow
• B. A physical break between two vessels
• C. A sealed barrier within a single vessel
• D. A flexible connector with a small clearance

Answer: (B)

Air gap separation is a physical break between the supply and the receiving vessel that prevents backflow. It creates an open air space, an unobstructed vertical distance, so water cannot be siphoned back because there’s no direct hydraulic connection between the two systems. This is different from a temporary seal, a sealed barrier inside a single vessel, or a flexible connector with a small clearance—none of those establish the atmospheric separation needed to prevent backflow. The key idea is the actual physical separation between two vessels, with air occupying the gap to stop backflow.