Backflow Prevention Practice Exam

What installation feature reduces the risk of contamination in a cross-connection?

1. Horizontal piping

2. Vertical separation

3. Air gap

4. Stagnant water

The correct answer is: Air gap

An air gap is a physical separation between the potable water supply and any potential source of contamination. This installation feature effectively prevents contaminated water from siphoning back into the clean water supply, which can occur in a cross-connection situation. The air gap is achieved when there is a vertical space between the water outlet and the highest point of the adjacent contaminant source, ensuring that contaminants cannot flow back into the system due to gravity or negative pressure. This method is widely recognized as one of the most reliable means of backflow prevention. The effectiveness of an air gap lies in its simplicity; it does not rely on mechanical components that can malfunction or require maintenance, making it a highly dependable solution in protecting water quality. Other options, while relevant in different contexts, do not offer the same level of security against contamination as an air gap does. Horizontal piping does not inherently create a barrier against backflow and may, in some cases, contribute to it. Vertical separation can potentially reduce the risk but does not provide a complete safeguard like an air gap. Stagnant water is contrary to the principles of backflow prevention, as it can create conditions ripe for contamination.