What shall the drainage and vent system be tested with if not using water?

The drainage and vent system can be tested with air if water is not used for the purpose of checking for leaks and ensuring the integrity of the system. Using air pressure testing is a common practice in plumbing to verify that the installed pipes and fittings are not leaking and can handle the necessary pressures without failure.

Air testing is favored because it is less cumbersome than water, especially for large systems, and it allows for immediate detection of leaks by creating a pressurized environment where any escaping air can signal a breach in the system. This technique often involves applying a specified pressure and maintaining that pressure for a determined amount of time, providing an efficient means of validation.

The other options—carbon dioxide, nitrogen, and steam—are not typically used for standard drainage and vent system testing. Carbon dioxide could pose safety risks due to its asphyxiating nature, nitrogen may not provide sufficient sensitivity for leak detection, and steam could introduce hazards and complications not present with air. Therefore, air testing remains the preferred method when water is not the chosen medium for testing drainage and vent systems.