Cross Connection Practice Exam

What term describes pressures less than that exerted by the atmosphere?

1. Vacuum

2. Negative Pressure

3. Low Pressure

4. Barometric Pressure

The correct answer is: Vacuum

The term that describes pressures less than that exerted by the atmosphere is "vacuum." In a vacuum, the pressure is significantly lower than atmospheric pressure, which is the force exerted by the weight of air in the atmosphere. This concept is essential in various applications, including plumbing and cross-connection control, as a vacuum can lead to backflow, where contaminants may enter the clean water supply. While "negative pressure" might seem relevant, it typically refers to a pressure that is lower than the surrounding pressure, often used in contexts such as ventilation systems. However, "vacuum" is the more specific term that encapsulates the condition of reduced pressure relative to atmospheric levels. "Low pressure" can describe a general condition but does not imply the absence of air molecules like a vacuum does. "Barometric pressure," on the other hand, specifically refers to the atmospheric pressure measured by a barometer and is not related to conditions of vacuum. Thus, the appropriate term for pressures below atmospheric levels is indeed vacuum.