In a piping system, what is the purpose of a vent?

• A. To seal joints
• B. To drain condensate
• C. To relieve trapped air and allow flow/pressure equalization
• D. To indicate flow direction

Answer: (C)

Vents in piping are used to release trapped air and equalize pressure so fluid can flow smoothly. When air is trapped in a line, it can form pockets that resist or block flow, create pressure surges, and even cause water hammer when flow starts or stops. By letting air escape at high points or at the top of a run, a vent prevents air locks and helps the system fill and operate consistently. This is why venting is important for efficient flow and pressure balance. It isn’t about sealing joints or draining condensate, and it doesn’t indicate flow direction.