Massachusetts Plumbers Journeyman Practice Exam

How many DFU (Drainage Fixture Units) are assigned to a Residential Full-Bath with Tank Type CW?

1. 4 DFU

2. 6 DFU

3. 8 DFU

4. 10 DFU

The correct answer is: 6 DFU

The assigned Drainage Fixture Units (DFU) for a residential full-bath with a tank-type water closet (WC) is typically considered to be 6 DFU. This value comes from plumbing code references that establish standardized fixture units for different types of plumbing installations. A full bathroom generally includes a water closet, sink, and possibly other fixtures like a bathtub or shower, but in the context of evaluating the DFU for the water closet specifically, it is commonly designated at 6 DFU. The value reflects the expected drainage load and associated factors like usage patterns and potential peak flow, which assist in properly sizing drainage systems. Understanding fixture unit counts is crucial for designing plumbing systems that manage waste effectively and ensure proper venting and drainage. The other potential values do not align with the most frequently used guidelines for calculating DFUs for a standard residential full-bath setup.