A plumber is adding a new washroom to an existing commercial building. The new washroom includes a water closet, a lavatory, and a floor drain. After installing the new drainage and vent piping, what type of test is typically performed by the plumber and verified by the inspector before the rough-in is approved?

Question: A plumber is adding a new washroom to an existing commercial building. The new washroom includes a water closet, a lavatory, and a floor drain. After installing the new drainage and vent piping, what type of test is typically performed by the plumber and verified by the inspector before the rough-in is approved?

Answer options:

• Air test at 34 kPa
• Smoke test at 100 Pa ✅ Water test to highest flood level rim
• Pressure test at 140 kPa

Correct answer: Water test to highest flood level rim

Explanation: According to the NPC, after the rough-in installation of drainage and vent piping, a water test is required. The system must be filled with water to the highest flood level rim of the fixtures, or to at least 3 m of head, and held for a specified duration (typically 15 minutes) with no leaks. An air test at 34 kPa is an alternative for drainage/venting but less common for rough-in, a smoke test is for leak detection in existing systems, and a pressure test at 140 kPa is typically for water distribution systems.