What is an “air gap”? Why are air gaps important? These were questions that a surveyor asked a food and nutrition staff member during a survey. In this instance the community was cited due inadequate air gaps. So, what is an air gap? An air gap is the area between the top of the floor drain to the bottom of the wastewater pipe. Air gaps must be 2 x the diameter of the drainpipe. For example, if a dishmachine had a 1-inch drainpipe, the air gap would have to be at least 2 inches. This is to eliminate or significantly reduce the likelihood of sewerage backflowing into the dishmachine, sinks, and other equipment that has a drainpipe. This same requirement is also for hand sinks and any other area where a drainpipe goes into an open drain. There is a picture below that shows where air gaps are located. If the air gap is not sufficient, maintenance or a plumbing service will need to correct the gap.