The air gap between the end of the faucet and the overflow rim of the sink should be how many times the diameter of the supply pipe?

An air gap is a critical component in plumbing systems, particularly in preventing backflow and maintaining safe drinking water standards. The requirement for the air gap between the end of the faucet and the overflow rim of the sink is specifically designed to prevent contaminants from entering the potable water supply. The recommended distance is two times the diameter of the supply pipe.

This two-to-one requirement works as a safety measure. If the faucet were to malfunction or if there were a drop in pressure in the supply line, the air gap ensures that any potential backflow of contaminated water is sufficiently prevented, as the water would need to rise twice the diameter of the pipe before it could potentially flow back into the drinking water supply.

Thus, choosing two times the supply pipe's diameter provides an effective barrier against contamination, ensuring public health safety in sanitation systems.