What is an unrestricted discharge from a Type AB air gap?

To be considered as providing fluid category 5 backflow protection, in addition to maintaining a suitable air gap, the water pathway to a Type AB air gap overflow, and discharge from the weir itself, must be unrestricted.

If the overflow is located close to another surface, such as a wall or other installation behind, in front or below the overflow, the gap between the discharge point and these surfaces must be sufficient to accommodate full discharge unimpeded. One way to demonstrate this is to ensure there is a clearance equivalent in shape and size to the weir overflow which is maintained to the air break to drain or floor level.