Red Seal Plumbing Practice Exam

What is the minimum size of a building drain?

1. 2" (50mm)

2. 3" (75mm)

3. 4" (100mm)

4. 5" (125mm)

The correct answer is: 3" (75mm)

The minimum size of a building drain is typically a 3" (75mm) diameter. This is because it ensures proper flow and drainage of waste and water from the building. Option A (2") is too small and may cause clogging and backups. Option C (4") and Option D (5") are larger than necessary and may result in higher construction costs. Therefore, the most practical and efficient choice is B (3"). Remember to always follow local building codes and regulations to determine the appropriate size for your specific project.