What component is essential for protecting potable water from contamination during filling operations?

The essential component for protecting potable water from contamination during filling operations is the air gap. An air gap is a vertical space between the water supply inlet and the overflow level of a receiving vessel, which effectively prevents backflow of contaminated water into the potable supply. It ensures that there is no physical connection that could allow any substance from the receiving vessel to siphon back into the clean water system, thereby maintaining the integrity of the drinking water.

This is particularly important during filling operations, where the risk of contamination is heightened due to potential back pressure or fluctuations in water levels. By providing that unobstructed vertical distance, an air gap is the most reliable method to prevent any possibility of cross-contamination, ensuring the water remains safe for consumption.

In contrast, other components like water meters, check valves, and strainers serve different functions in a water system. While water meters measure flow, check valves prevent reverse flow but may still be susceptible to issues if not properly maintained, and strainers are used to filter out debris but do not prevent contamination through backflow. Hence, the air gap stands out as the critical protective measure against potential contamination.