Backflow Prevention Practice Exam

What type of backflow preventer uses a physical separation to maintain water quality?

1. Check valve

2. Air gap

3. Reduced pressure zone

4. Ball valve

The correct answer is: Air gap

The backflow preventer that maintains water quality through a physical separation is the air gap. An air gap is an unobstructed vertical space, typically at least two inches, between the highest point of a liquid’s source and the level of the flood rim of the receptacle it's filling. This separation effectively prevents any backflow or reverse siphoning of contaminated water into the potable water supply because it creates a physical barrier that cannot be overcome by pressure changes in the system. In contrast, other options such as a check valve, reduced pressure zone, and ball valve rely on mechanical components to prevent backflow, which may not provide the same level of assurance against contamination as the air gap. While these devices are effective in many situations, they do not create a physical separation from the water supply, making them less robust in certain high-risk applications where contamination could occur. Therefore, the air gap is the preferred choice for ensuring water quality in situations that require a high level of protection against backflow.