Which device is specifically used to prevent pipe collapse during emptying and is often installed to relieve air and vacuum?

• A. Air and vaccum relief valve
• B. Pressure relief valve
• C. Check valve
• D. Gate valve

Answer: (A)

The device is designed to prevent negative pressure in the line as it’s emptied, which can cause pipe collapse, by letting air move in and out as needed. An air and vacuum relief valve specifically handles both releasing trapped air during filling and admitting air when a vacuum would form during emptying. By providing a controlled path for air to escape and then enter, it keeps the internal pressure from dropping below ambient and protects the pipe from collapse, especially at high points or dead-ends where air pockets and vacuum are most likely to develop.

Other devices serve different functions: a pressure relief valve protects against overpressure, a check valve prevents backflow, and a gate valve is simply a shut-off valve. None of those addresses vacuum and air management in the way an air and vacuum relief valve does.