How much air gap is required above the rim of a sink and a faucet?

The correct answer, which indicates that there should be an air gap of either 1 inch or twice the diameter of the faucet above the rim of a sink, is based on the principles of backflow prevention. The air gap is a critical component designed to prevent contamination of the potable water supply by ensuring there is adequate space between the faucet and the sink.

The rationale behind this requirement stems from the need to thwart back-siphonage, which can occur when a drop in water pressure allows potentially contaminated water from the sink to be drawn back into the clean water supply. By maintaining this specific distance, it ensures that there is sufficient separation that prevents such cross-contamination from happening.

This requirement is consistent across various plumbing codes and health regulations, which emphasize the importance of backflow prevention in maintaining safe drinking water standards in food service and hospitality industries.