Each assembly has different features and purposes. Choose an assembly that meets your needs.
An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel. This separation must be at least twice the diameter of the water supply outlet and never less than one inch. An air gap is considered the maximum protection available against backpressure backflow or backsiphonage, but is not always practical and can easily be bypassed.
Details about this system include:
Not always practical
Use of an air gap often exposes water to dust, debris, airborne bacteria, and other contaminants and pollutants