Plumber Red Seal · Question
Why is a "double trap" or "S-trap" prohibited by modern plumbing codes?
S-traps create a full siphon during drainage that can pull all the water out of the trap. This breaks the trap's water seal, allowing dangerous sewer gases to e
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Question: Why is a "double trap" or "S-trap" prohibited by modern plumbing codes?
Answer options:
- They are exceptionally difficult to clean out. ✅ They are prone to self-siphonage, which removes the trap seal.
- They require too much vertical space to install.
- They create excessive noise during operation.
Correct answer: They are prone to self-siphonage, which removes the trap seal.
Explanation: S-traps create a full siphon during drainage that can pull all the water out of the trap. This breaks the trap's water seal, allowing dangerous sewer gases to enter the building. Modern P-traps with proper venting prevent this.
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