Backflow Prevention Practice Exam

Which installation condition is least likely to require an atmospheric vacuum breaker?

1. Sloping drainage

2. Submerged outlets

3. Closed tanks

4. Elevated systems

The correct answer is: Elevated systems

An atmospheric vacuum breaker is designed to prevent backflow due to back siphonage in a system, typically by allowing air to enter the line and break the vacuum. Elevated systems, such as those where water is supplied from a height, usually maintain a constant pressure due to gravity and are less susceptible to creating a vacuum that would necessitate the installation of an atmospheric vacuum breaker. In contrast, sloping drainage systems can often facilitate the movement of fluids in a way that might create conditions for back siphonage, making the need for a vacuum breaker more critical. Submerged outlets present a higher risk of backflow since the outlet is below the water level, increasing the potential for contamination. Similarly, closed tanks may create pressure changes that could lead to back siphonage, justifying the need for protection against it. Elevated systems, however, typically do not encounter conditions that would lead to a backflow scenario that an atmospheric vacuum breaker would mitigate, making them the least likely installation condition for such a device.