Any potable water supply going to a pressure sewer waste shall be through what?

The correct choice is the air gap because it provides the highest level of protection against contamination of the potable water supply. An air gap acts as a physical barrier between the potable water supply and the potential sources of contamination found within the pressure sewer system. By creating a distinct and separate space between the two systems, an air gap prevents backflow — the undesirable reverse flow of non-potable water back into the drinking water supply.

This method of protection is critical in maintaining water quality and safety standards, particularly in situations where there is a risk of sewer backflow that could introduce harmful pathogens or pollutants into the potable water system. In many plumbing codes and regulations, air gaps are specified in instances where there's an elevated risk of cross-connection, making them essential for protecting health and safety in water supply systems.

While other devices like reduced pressure backflow preventers and double check valve assemblies are also utilized to prevent backflow, they might not provide the same level of security as an air gap in scenarios involving wastewater systems. Regular valves, on the other hand, are not designed to provide backflow prevention features and therefore would not suffice in a setting requiring strict protection against contamination.