What is the primary reason for high-point vents in hydrotesting?

• A. To vent water
• B. To measure pressure
• C. To purge air pockets
• D. To test pipe strength

Answer: (C)

High-point vents are used to purge air pockets from a piping system during hydrotesting. When the system is filled with water from the bottom, air tends to collect at the highest points. These trapped air pockets compress under pressure, prevent a full and uniform water fill, distort pressure readings, and can mask leaks or cause water hammer. By venting at the high points, the air escapes as the system fills and pressurizes, until water reaches the vents and the line is completely water-filled. This makes the test reliable because you’re measuring the true integrity of the pipe rather than artifacts from air.