How are air gaps measured in relation to a potable water outlet?

Measuring air gaps in relation to a potable water outlet is essential for preventing contamination of the drinking water supply. The correct answer identifies that air gaps are measured from the flood level rim. This is significant because the flood level rim represents the highest point at which water can fill a fixture without overflowing. By measuring from this rim, you establish a clear and consistent reference point to ensure that any backflow or potential siphoning effect is effectively mitigated.

In practice, the air gap must be maintained at a specific height above the flood level rim to ensure that any contaminants cannot flow back into the potable water supply, thus safeguarding public health. This measurement is critical in plumbing codes and regulations to create a safe and compliant water system within buildings.

The other options are not suitable reference points for measuring air gaps. For example, measuring from the spout or the outlet nozzle does not account for the potential overfilling of the fixture, which could compromise the safety of the water supply. Similarly, measuring from the water surface does not ensure a safe distance from potential backflow risks, making it inappropriate for assessing air gaps as per plumbing guidelines.