Plumber Red Seal · Question
What is the minimum grade (slope) for a 4-inch horizontal sanitary building drain according to the NPC?
According to the NPC Table 2.4.10.1.A, the minimum slope for a 4-inch or larger horizontal sanitary drainage pipe is 1 in 100 (1%). Pipes 3 inches or smaller re
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Question: What is the minimum grade (slope) for a 4-inch horizontal sanitary building drain according to the NPC?
Answer options:
- 1 in 200 (0.5%) ✅ 1 in 100 (1%)
- 1 in 50 (2%)
- 1 in 25 (4%)
Correct answer: 1 in 100 (1%)
Explanation: According to the NPC Table 2.4.10.1.A, the minimum slope for a 4-inch or larger horizontal sanitary drainage pipe is 1 in 100 (1%). Pipes 3 inches or smaller require a minimum slope of 1 in 50 (2%) to ensure sufficient flow velocity.
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