What is the minimum time a smoke test must be maintained to verify gas-tightness of a DWV system?

• A. 10 minutes
• B. 15 minutes
• C. 20 minutes
• D. 30 minutes

Answer: (B)

The minimum time a smoke test must be maintained to verify the gas-tightness of a Drainage, Waste, and Vent (DWV) system is 15 minutes. This duration is established to ensure that any potential leaks within the system can be adequately detected. A smoke test involves introducing a smoke-producing substance into the DWV system, and by maintaining the test for a sufficient period, inspectors can observe any escaping smoke, which would indicate deficiencies in the system’s integrity.

Maintaining the smoke test for 15 minutes allows for a thorough inspection of the system under varying conditions, ensuring all components are capable of holding gases without leakage. This practice aligns with standard plumbing codes and guidelines aimed at ensuring the safety and efficiency of plumbing systems in residential properties.