The Big Dipper HAG-2 Horizontal Air Gap Assembly Kit offers a simple yet effective method for providing an air gap for meeting health department or plumbing code requirements. Among the many different methods of creating an air gap to protect against cross-contamination, the most popular is an air gap directly between the sink discharge and the outflow piping. In the event of a backup, effluent will spill out of this gap under the sink and directly onto the floor without any danger of cross-contamination.