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

The purpose of an air gap in plumbing systems is to ensure sanitary drainage. An air gap is a physical separation between two systems, typically between the outlet of a fixture, like a faucet, and the flood level of a receiving vessel, such as a sink. This separation prevents the possibility of backflow or contamination, ensuring that waste and harmful substances do not enter the potable water supply.

By creating a space where no physical connection exists, the air gap acts as a barrier, allowing drainage without the risk of contaminated water being siphoned back into the clean water system. This is critically important for maintaining public health and safety, as it minimizes the risk of cross-connection between drinking water and sewage or drainage systems.

Other options do not accurately describe the function of an air gap; it does not primarily deal with air escaping or facilitating water flow. Maintaining pressure is also not relevant as it pertains to the function of an air gap.