Journeyman Plumber ExamFixtures, Faucets, and Other AppliancesMedium
A client is replacing a standard kitchen sink with a new triple-bowl sink that includes a garbage disposal in one of the bowls. The existing drain line is 1 1/2 inches. What is the minimum required drainage fixture unit (DFU) value for a kitchen sink with a garbage disposal?
- A3 DFU
- B4 DFU
- C1 DFU
- D2 DFU
Show answer & explanationAnswer & explanation
Correct answer: A. 3 DFU
According to the Uniform Plumbing Code (UPC) and International Plumbing Code (IPC), a kitchen sink with a garbage disposal is assigned a DFU value of 3. This accounts for the increased waste load and potential for solids.
Why the other options are wrong
- B. 4 DFU is usually for a water closet or a combination of fixtures with significant drainage requirements.
- C. 1 DFU is typically for a lavatory or small bar sink.
- D. 2 DFU is common for a standard kitchen sink without a disposal or a washing machine.
Kitchen Sink DFU (with Disposal)
The drainage fixture unit value assigned to a kitchen sink when equipped with a garbage disposal, indicating its relative load on the drainage system.
- DFU values are used to size drain, waste, and vent piping.
- A garbage disposal increases the DFU value due to added solids.
- Specific DFU values are found in plumbing code tables (e.g., IPC Table E103.3(2)).
Memory trick: DFUs are like weight classes for drains; bigger fixtures need bigger numbers.