Food waste disposers must have a supply of cold water protected against backflow by what?

Food waste disposers require a supply of cold water that is protected against backflow to ensure that contaminated water does not flow back into the potable water supply. The correct method for this protection is through an air gap.

An air gap is a physical separation between the end of a water supply outlet and the flood level rim of a fixture, effectively preventing backflow by maintaining a space where water cannot travel. In the case of food waste disposers, the air gap allows for proper drainage while ensuring that any waste or contaminants from the disposer cannot siphon back into the clean water line.

This is crucial for maintaining the safety and quality of the drinking water supply, and it complies with the plumbing code requirements for sanitary plumbing systems, which stipulate that cross-connections must be prevented to avoid health hazards.