Journeyman Plumber ExamPlumbing Code and RegulationsMedium
A plumber is calculating the total fixture units for a new commercial restroom. The restroom includes two water closets, two lavatories, and one floor drain. According to the Uniform Plumbing Code (UPC), what is the total drainage fixture unit (DFU) count for these fixtures?
- A8 DFU
- B12 DFU
- C14 DFU
- D10 DFU
Show answer & explanationAnswer & explanation
Correct answer: D. 10 DFU
According to UPC Chapter 7, a water closet (private) is 4 DFU, a lavatory (private/public) is 1 DFU, and a floor drain is 2 DFU. Therefore, (2 water closets * 4 DFU) + (2 lavatories * 1 DFU) + (1 floor drain * 2 DFU) = 8 + 2 + 2 = 12 DFU.
Why the other options are wrong
- A. Incorrect calculation; undercounts the total DFU.
- B. 12 DFU is the correct total: (2 x 4 DFU for water closets) + (2 x 1 DFU for lavatories) + (1 x 2 DFU for floor drain) = 8 + 2 + 2 = 12 DFU.
- C. Incorrect calculation; overcounts the total DFU.
Drainage Fixture Unit (DFU) Calculation
A measure of the probable discharge into the drainage system by various plumbing fixtures, used to size drainage piping.
- Each fixture assigned a DFU value.
- Values differ slightly between UPC and IPC.
- Total DFU determines pipe size and vent requirements.
Memory trick: DFU: Drainage Flow Units, Find the Sum, Pipe for Fun!