Backflow Prevention Practice Exam

What type of backflow preventer is most effective at preventing backsiphonage?

1. Air gap

2. Double check valve

3. Installed strainer

4. Pressure relief valve

The correct answer is: Air gap

An air gap is the most effective backflow preventer specifically designed to protect against backsiphonage. Backsiphonage occurs when there is a negative pressure in the system, which can draw contaminants back into the potable water supply, particularly in scenarios where there is a sudden drop in water pressure. The air gap acts as a physical barrier preventing contaminated water from flowing back into the clean water supply. It does this by ensuring there is a vertical distance between the water supply outlet and the highest point of potential contamination. This separation is crucial because it eliminates the possibility of contaminated water reaching the outlet in the event of backsiphonage, making it the most reliable form of protection. In contrast, other types of backflow prevention devices, such as double check valves, may provide a level of protection against backpressure but are less effective in situations involving backsiphonage. A double check valve requires proper maintenance and testing to ensure optimal functionality. Similarly, an installed strainer is primarily used to filter debris and thus does not prevent backflow. A pressure relief valve may manage the pressure in a system but does not specifically address the risks associated with backsiphonage. Therefore, the air gap is uniquely effective in safeguarding against this particular type of back