Clothes Washer Drainage Fixture Units (DFU) value is?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (C)

DFU numbers are how codes size drainage by assigning a fixed load to each fixture. The clothes washer is given a DFU of 3, reflecting its typical discharge rate and how it contributes to the drainage system. This value is used when sizing the waste line: you add the DFUs of all fixtures on a branch and then consult the table to determine the required pipe size. So, the clothes washer drainage has a DFU value of 3 because that’s the standard table value for this fixture, balancing its flow characteristics with the sizing rules.