Plumber Red Seal · Question
A plumber is roughed in a two-storey commercial washroom. On the second floor, there are four water closets and four lavatories. The soil stack for these fixtures is 102 mm (4 inches) in diameter. What is the minimum required diameter for the main vent stack considering the number and type of fixtures and the soil stack size?
According to the National Plumbing Code, a 102 mm (4 inch) soil stack serving multiple water closets typically requires a 64 mm (2 1/2 inch) minimum diameter ma
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Question: A plumber is roughed in a two-storey commercial washroom. On the second floor, there are four water closets and four lavatories. The soil stack for these fixtures is 102 mm (4 inches) in diameter. What is the minimum required diameter for the main vent stack considering the number and type of fixtures and the soil stack size?
Answer options:
- 51 mm (2 inches) ✅ 64 mm (2 1/2 inches)
- 76 mm (3 inches)
- 102 mm (4 inches)
Correct answer: 64 mm (2 1/2 inches)
Explanation: According to the National Plumbing Code, a 102 mm (4 inch) soil stack serving multiple water closets typically requires a 64 mm (2 1/2 inch) minimum diameter main vent stack. This sizing ensures adequate air circulation for the drainage system.
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