One of the more dangerous plumbing mistakes is when there is a potential cross connection between the potable water supply system and nonpotable liquids, solids, or gases! This is a very serious issue that can and has caused thousands of individuals to get sick and/or die. A airgap is one of the best forms of backflow prevention. An airgap makes sure that the nonpotable water is not close enough to the water outlet that if there were a break in the water line where that the dirty water can be sucked back into the water supply system. The code P2902.3.1 in the 2021 IRC states that the airgap or space between the water outlet and the flood level rim shall not be less that twice the diameter of the effective opening of the outlet and not less than the values specified in Table P2902.3.1. Can you see the problem in the picture above?