Final answer:
An air gap fitting is used to prevent backflow into appliances like dishwashers by creating a vertical separation between the wastewater system and any openings that contact drinkable water.
Step-by-step explanation:
An air gap fitting is a fitting that creates a vertical separation and prevents backflow into an appliance such as a dishwasher. It is not an air admittance valve, backflow preventer, offset, or appliance vent. The primary function of an air gap fitting is to ensure that there is no direct connection between the waste-water system and any rim-level openings that contact potable water. In this way, the air gap prevents contamination of the water supply. For instance, in the case of a dishwasher, an air gap fitting is typically mounted above the sink level to prevent sink water from siphoning back into the dishwasher. This is an important health and safety feature that protects against water contamination.