Journeyman Plumber ExamFixtures, Faucets, and Other AppliancesEasy
A plumber is installing a new bathtub in a residential bathroom. What is the minimum required diameter for the trap and trap arm serving this fixture?
- A1 1/2 inches
- B3 inches
- C1 1/4 inches
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 1 1/2 inches
According to most plumbing codes, bathtubs require a minimum trap and trap arm diameter of 1 1/2 inches to ensure adequate drainage and prevent clogging.
Why the other options are wrong
- B. 3 inches is generally for water closets or main drain lines, not individual fixtures like bathtubs.
- C. 1 1/4 inches is typically used for lavatories, not bathtubs.
- D. 2 inches is usually for showers or kitchen sinks, which have higher drainage requirements.
Bathtub Trap Diameter
The minimum internal diameter required for the trap and trap arm connected to a bathtub.
- Ensures proper drainage and waste removal.
- Prevents clogs and maintains trap seal.
- Mandated by plumbing codes like IPC and UPC.
Memory trick: Each fixture has a specific pipe size, like shoes for different feet.