What is the maximum Drainage Fixture Units (DFUs) allowed on a 2-inch horizontal waste line?

What is the maximum Drainage Fixture Units (DFUs) allowed on a 2-inch horizontal waste line?

• A. 6 DFUs
• B. 4 DFUs
• C. 8 DFUs
• D. 10 DFUs

Answer: (A)

In drainage design, the load a fixture places on a horizontal waste line is measured in drainage fixture units (DFUs), and the code provides a table that limits how many DFUs a given pipe size can carry on a horizontal run. For a 2-inch horizontal waste line, the maximum allowed is six DFUs. This means you add up the DFU values of every fixture draining into that line, and as long as the total is six or less, the 2-inch line is acceptable. If adding another fixture would push the total above six, you’d need a larger pipe or a different routing to maintain proper drainage and venting. The exact DFU values per fixture vary by type, but the guiding rule is clear: keep the total on that 2-inch run at six DFUs or fewer.

In drainage design, the load a fixture places on a horizontal waste line is measured in drainage fixture units (DFUs), and the code provides a table that limits how many DFUs a given pipe size can carry on a horizontal run. For a 2-inch horizontal waste line, the maximum allowed is six DFUs. This means you add up the DFU values of every fixture draining into that line, and as long as the total is six or less, the 2-inch line is acceptable. If adding another fixture would push the total above six, you’d need a larger pipe or a different routing to maintain proper drainage and venting. The exact DFU values per fixture vary by type, but the guiding rule is clear: keep the total on that 2-inch run at six DFUs or fewer.