An AB weir air gap sits directly below the water discharge point and stops contaminated water mixing with mains water.

If a vacuum occurs in the supply pipe, this backflow prevention device draws in air, rather than stored water.

Its size depends on the size of the supply pipe coming into the cistern. Once you know your supply pipe’s internal diameter, you can decide whether to use an unobstructed weir or one with a mesh over it.

 

Below are the weir dimensions for an AB air gap.

Find out more here.

 

Further information

File icon Weir calculator