During drain and vent system testing, which gauge pressure is used for the air test?

• A. 2 PSI
• B. 5 PSI
• C. 10 PSI
• D. 15 PSI

Answer: (B)

The air test for a drain and vent system is performed at a low gauge pressure of 5 psi. This pressure is high enough to reveal leaks in joints and fittings when the system is pressurized, yet low enough to avoid stressing pipes, joints, or traps. In practical terms, 5 psi corresponds to about 11.5 feet of water column, which provides a reliable leak-check without risking damage. To test, you seal the system, pressurize it to 5 psi, and hold the pressure for the Code-specified duration while checking for any drop in pressure that would indicate a leak. Pressures like 2 psi are usually not sufficient to reveal leaks, while higher pressures (10 or 15 psi) can unnecessarily stress the system.