Journeyman Plumber ExamFixtures, Faucets, and Other AppliancesMedium
A plumber is installing a new kitchen sink with a single basin and a garbage disposal. According to the Uniform Plumbing Code (UPC), what is the minimum trap size required for this combination?
- A2 inches
- B2 1/2 inches
- C1 1/2 inches
- D1 1/4 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 1 1/2 inches
For a kitchen sink, whether single or double basin, and especially when including a garbage disposal, the minimum trap size required by the Uniform Plumbing Code (UPC) is 1 1/2 inches. This size is necessary to handle the typical flow rates and potential waste from a kitchen sink and disposal.
Why the other options are wrong
- A. 2 inches is often used for bathtubs, showers, or larger fixtures, exceeding the minimum for a standard kitchen sink.
- B. 2 1/2 inches is not a common trap size for residential kitchen sinks.
- D. 1 1/4 inches is typically used for lavatories or smaller fixtures, not kitchen sinks.
Kitchen Sink Trap Size
The minimum diameter of the P-trap required for a kitchen sink, typically 1 1/2 inches, especially with a garbage disposal.
- Determined by plumbing code (UPC/IPC).
- Ensures adequate drainage and prevents clogs.
- Larger traps are generally for higher flow fixtures.
Memory trick: Kitchen's flow needs one-and-a-half to go.