What does an air gap provide in a water supply system?

An air gap provides a physical separation between the water supply and any potential contaminants, making it an essential feature in preventing backflow. Backflow can occur when there is a change in pressure within the system, potentially allowing contaminated water to flow back into the clean water supply. The air gap acts as a safeguard by ensuring that there is a substantial distance—typically several inches—between the end of a water supply outlet and the upstream source of contamination. This separation effectively eliminates the risk of backflow, as contaminants cannot travel over the gap and re-enter the potable water system. In this way, an air gap is a critical safety measure in plumbing design to maintain water quality and ensure public health.