Final answer:
An air gap is the air space between an outlet of drinkable water and any potentially contaminated source, acting as a physical barrier to prevent contamination of the clean water supply. It is required by plumbing codes for health and safety reasons.
Step-by-step explanation:
An air gap is the air space between an outlet of drinkable water and any potentially contaminated source. This air space is crucial because it prevents the backflow of contaminated water into the clean water supply, which could lead to health issues if consumed. Plumbing systems often include air-filled tubes near water faucets to create this air gap. When water flows from the main supply to the faucet, the air gap stops any reverse flow of dirty water due to back-siphonage or backpressure.
The air gap works as a simple, yet effective physical barrier. For example, in the case of a sink, if the sink were to overfill, the water would still need to overcome the air gap before it could potentially contaminate the clean water supply. In plumbing codes, ensuring an air gap is a critical requirement for maintaining public health standards and safety.