Backflow Prevention Practice Exam

What happens to gauge pressure when the water velocity increases?

1. Atmospheric pressure decreases

2. Gauge pressure decreases

3. Gauge pressure increases

4. Head loss does not change

The correct answer is: Gauge pressure decreases

When water velocity increases in a pipeline, gauge pressure behavior is influenced by the principles of fluid dynamics, specifically Bernoulli's principle. According to this principle, as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Gauge pressure, which measures pressure relative to atmospheric pressure, reflects these changes. Therefore, when water flows faster, the kinetic energy of the water increases, leading to a corresponding decrease in gauge pressure at that point in the system. The relationship between velocity and pressure is critical in understanding backflow prevention systems, as it helps identify how variations in flow can affect the overall pressure dynamics within the system. As the velocity increases, the decreased gauge pressure can influence the effectiveness of backflow prevention devices, which rely on specific pressure conditions to operate correctly.