A plumber is installing new water distribution piping for a small commercial building with three washrooms, each containing a water closet, a lavatory, and a service sink. The building also has a staff kitchen with a single-basin sink. Based on the National Plumbing Code of Canada, what is the minimum total fixture unit value for sizing the main cold water service line?

Question: A plumber is installing new water distribution piping for a small commercial building with three washrooms, each containing a water closet, a lavatory, and a service sink. The building also has a staff kitchen with a single-basin sink. Based on the National Plumbing Code of Canada, what is the minimum total fixture unit value for sizing the main cold water service line?

Answer options:

• 28 fixture units ✅ 24 fixture units
• 20 fixture units
• 16 fixture units

Correct answer: 24 fixture units

Explanation: According to the National Plumbing Code of Canada (NPC), a water closet with a flush tank has 3 fixture units, a lavatory has 1 fixture unit, and a service sink has 3 fixture units. A single-basin kitchen sink has 2 fixture units. For three washrooms, this totals (3x3) + (3x1) + (3x3) = 9 + 3 + 9 = 21 fixture units. Adding the staff kitchen sink (2 fixture units) results in a total of 23 fixture units. The closest option above is 24 fixture units, as fixture unit calculations often round up or use tables that jump in increments.