What is the recommended air gap to prevent backflow contamination of the potable water supply?

AIR GAP — BACKFLOW PREVENTION: An air gap is a physical vertical space between a water supply outlet and the flood rim level of the receiving vessel (sink, equipment). It prevents BACKFLOW — the reverse flow of contaminated water into the potable (drinking) water supply, which can occur when pressure drops (back-siphonage) or when downstream pressure exceeds supply pressure (backpressure); RECOMMENDED AIR GAP: At least twice the diameter of the supply pipe opening, and never less than 1 inch; CROSS-CONNECTION: A direct connection between potable and non-potable water (a hose submerged in a mop bucket, a dishwasher drain connected directly to a sewer line) is a contamination hazard; PREVENTION METHODS: Air gaps (most reliable); backflow prevention devices/vacuum breakers; PLUMBING is a critical sanitation area — improper plumbing can contaminate the entire water supply; food managers must ensure proper air gaps on sinks, dishwashers, and equipment, and prevent cross-connections; this protects against waterborne illness.