Type AA air gap – air gap with unrestricted discharge

A non-mechanical backflow prevention arrangement of water fittings where water is discharged through an air gap into a receptacle which has at all times an unrestricted spillover to atmosphere. 

Maximum permissible fluid category against which a Type AA air gap is accepted as adequate backflow protection:

Backflow by back pressure: fluid category 5

Backflow by back siphonage: fluid category 5

Interpretation given in Regulators’ Backflow Specification - backflow prevention arrangements and devices: backflow prevention arrangements