What is the primary purpose of an air gap in plumbing systems?

The primary purpose of an air gap in plumbing systems is to prevent the mixing of potable (drinking) and non-potable (non-drinking) water. This physical separation creates a space between the outlet of a fixture, such as a faucet or hose, and the flood level of a fixture or receptacle. This is crucial for maintaining water quality and ensuring that contaminated water cannot flow back into the clean drinking water supply due to back siphonage or backflow.

In practice, air gaps are implemented in various installations where there is a potential risk of contamination, such as kitchen sinks, dishwashers, and bathroom sinks, to protect the health and safety of the water supply by adhering to plumbing codes and regulations. By preventing the possibility of non-potable water mixing with potable sources, air gaps effectively safeguard public health.