A vacuum breaker is used to avoid which pressure condition?

A vacuum breaker is used to avoid which pressure condition?

• A. Negative absolute pressure
• B. Negative gauge pressure
• C. Positive absolute pressure
• D. Positive gauge pressure

Answer: (B)

A vacuum breaker is meant to prevent the system from developing a vacuum, which occurs when the pressure in the line falls below the surrounding atmospheric pressure. That situation is negative gauge pressure (pressure below atmosphere). Absolute pressure can’t be negative in normal conditions, so the idea of a “negative absolute pressure” isn’t applicable here. The device works by letting air into the line when pressure drops, breaking the vacuum and preventing back-siphonage or backflow of contaminated water. Positive pressures (absolute or gauge) aren’t the issue vacuum breakers address, since they’re about avoiding vacuum formation rather than overpressure.

A vacuum breaker is meant to prevent the system from developing a vacuum, which occurs when the pressure in the line falls below the surrounding atmospheric pressure. That situation is negative gauge pressure (pressure below atmosphere). Absolute pressure can’t be negative in normal conditions, so the idea of a “negative absolute pressure” isn’t applicable here. The device works by letting air into the line when pressure drops, breaking the vacuum and preventing back-siphonage or backflow of contaminated water. Positive pressures (absolute or gauge) aren’t the issue vacuum breakers address, since they’re about avoiding vacuum formation rather than overpressure.