Core TradesQuestion 185 of 700
Limiting the developed length of a fixture's trap arm (the distance from the trap to its vent) is important PRIMARILY to:
a.Prevent the trap from losing its water seal by self-siphonage
b.Increase the flow rate through the fixture
c.Reduce the amount of pipe material used
d.Allow the trap to be installed without a cleanout
Explanation
Keeping the trap arm within its maximum length prevents self-siphonage that would pull the water seal out of the trap and let sewer gas enter. It is not primarily about saving pipe, boosting flow, or avoiding cleanouts.
Law Reference: 2025 CA Plumbing Code, Chapter 9 (Vents)Practice all 700 questions free — no signup required.
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