What is considered the best way to prevent cross-connection contamination in a water supply?

The best way to prevent cross-connection contamination in a water supply is to implement an air gap. An air gap is a physical separation between the water supply and any potential source of contamination. This involves creating a vertical distance between the drinking water outlet and the highest point of potential contamination, which eliminates the possibility of backflow, where contaminated water could siphon back into the potable water system.

By maintaining an air gap, the potential for contaminants to enter the drinking supply through pressure changes or other disturbances is effectively neutralized. This method is straightforward and relies on gravity, making it a dependable barrier against contamination without the mechanics and maintenance requirements that other systems may have.

In contrast, a backflow preventer, while effective in many situations, is a mechanical device that relies on proper function and maintenance to avoid backflow conditions. A check valve is also a mechanical device that prevents backflow but shares some of the same vulnerabilities as backflow preventers. A filtration system can reduce contaminants in water but does not inherently prevent cross-connections from occurring. Hence, while these methods are useful for various applications, the air gap stands out as the most reliable and failsafe approach to preventing cross-connection contamination.