What is the primary function of an air/vacuum relief valve in irrigation piping?

• A. Releases trapped air and prevents vacuum during system startup
• B. Controls flow rate and pressure
• C. Measures soil moisture content
• D. Reduces wind drift from sprinklers

Answer: (A)

Air/vacuum relief valves manage air and negative pressure in irrigation lines, especially during fill and shutdown. Their main job is to vent trapped air so the system can fill evenly and to prevent the formation of a vacuum that could pull on the piping as water is drawn in or drains out. By opening to release air as the line fills, they help avoid air pockets that would block flow and cause irregular pressure surges. When pressure drops suddenly, the valve can admit air to prevent negative pressure from collapsing piping or joints. This function keeps the system from problems like water hammer and pipe damage, and it’s not about controlling flow or pressure, measuring soil moisture, or reducing wind drift.