The most reliable form of backflow prevention device is a/an?

An air gap is considered the most reliable form of backflow prevention device because it creates a physical separation between the source of contamination and the potable water supply. This gap prevents any backflow from occurring, as it ensures that no liquid can travel back from a contaminated source to the clean water supply. The air gap must be at least twice the diameter of the water supply outlet to be effective.

This method does not rely on mechanical components, which can fail over time or become contaminated themselves, making it a fail-safe solution for preventing backflow issues. An air gap is commonly used in applications where the risks of contamination are significant, such as in kitchen sink installations or when filling water storage tanks, ensuring the highest safety level in food handling environments.