What is an air gap in a water distribution system?

An air gap in a water distribution system refers to the unobstructed vertical distance between the end of a supply pipe and the flood level rim of a receptacle or fixture. This gap acts as a crucial safety feature, preventing the backflow of contaminated water into the potable water supply.

The air gap ensures that, in the event of a pressure drop or reverse flow in the system, there is no direct connection between the water supply and potential contaminants, thereby maintaining the integrity of the drinking water. This is particularly important in plumbing installations where there is a risk of siphoning or backpressure, such as sinks, toilets, or hoses submerged in containers.

Other choices, while related to plumbing, do not define an air gap accurately. For instance, a backflow preventer can include various devices, and while it may provide some level of protection, it does not specifically denote the defined air space required by an air gap. A valve used in drainage pertains to controlling flow in pipes rather than the concept of an air gap. A measure of water pressure does not relate to the physical distancing principle that an air gap represents. Thus, understanding the air gap in the context of safe plumbing practices emphasizes its role in protecting water quality.