Plumber Red Seal · Question
What is the minimum trap seal depth required for a standard P-trap under the National Plumbing Code?
The NPC specifies that a fixture trap must have a water seal depth of not less than 38 mm (1.5 inches). This depth is sufficient to block sewer gas from enterin
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Question: What is the minimum trap seal depth required for a standard P-trap under the National Plumbing Code?
Answer options:
- 25 mm ✅ 38 mm
- 50 mm
- 76 mm
Correct answer: 38 mm
Explanation: The NPC specifies that a fixture trap must have a water seal depth of not less than 38 mm (1.5 inches). This depth is sufficient to block sewer gas from entering the building while being shallow enough to be scoured clean by normal fixture use.
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