A plumber is tasked with installing a laundry tub and washing machine in a residential basement. Both fixtures will drain into a 50 mm branch drain. What is the minimum required drainage unit (DU) load for this section of the branch drain, according to the NPC, to ensure adequate capacity?

Question: A plumber is tasked with installing a laundry tub and washing machine in a residential basement. Both fixtures will drain into a 50 mm branch drain. What is the minimum required drainage unit (DU) load for this section of the branch drain, according to the NPC, to ensure adequate capacity?

Answer options:

• 2 DUs
• 3 DUs
• 4 DUs ✅ 5 DUs

Correct answer: 5 DUs

Explanation: According to the National Plumbing Code of Canada (NPC), an automatic washing machine typically has a drainage unit (DU) load of 2, and a laundry tub has a DU load of 3. Therefore, the minimum required drainage unit load for this section of the branch drain would be 2 + 3 = 5 DUs. A 50 mm branch drain can accommodate up to 6 DUs.