A vacuum breaker is used to avoid which condition?

A vacuum breaker is used to avoid which condition?

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

Answer: (B)

A vacuum breaker protects the system from backflow when downstream pressure falls below atmospheric, creating a vacuum-like condition. It does this by admitting air into the line to break the siphon, so contaminated water can’t be drawn back into the supply. This specifically targets a negative gauge pressure (pressure below ambient). Absolute pressure, while not negative in physical terms, isn’t what this device addresses, and positive pressures don’t pose the same siphon risk.

A vacuum breaker protects the system from backflow when downstream pressure falls below atmospheric, creating a vacuum-like condition. It does this by admitting air into the line to break the siphon, so contaminated water can’t be drawn back into the supply. This specifically targets a negative gauge pressure (pressure below ambient). Absolute pressure, while not negative in physical terms, isn’t what this device addresses, and positive pressures don’t pose the same siphon risk.