When installing a 100 mm horizontal drainage piping, what is the minimum slope required to ensure adequate self-scouring velocity and prevent solid accumulation, as per the National Plumbing Code of Canada?

Question: When installing a 100 mm horizontal drainage piping, what is the minimum slope required to ensure adequate self-scouring velocity and prevent solid accumulation, as per the National Plumbing Code of Canada?

Answer options: ✅ 1% (10 mm/m)

• 2% (20 mm/m)
• 4% (40 mm/m)
• 6% (60 mm/m)

Correct answer: 1% (10 mm/m)

Explanation: For horizontal drainage piping equal to or larger than 75 mm in diameter, the National Plumbing Code of Canada requires a minimum slope of 1% (10 mm per metre). Smaller diameter pipes require a steeper slope (e.g., 2% for 50 mm pipes).