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Engineering ToolBox > Drainage Fixture Unit Loads for Sanitary Piping
The maximum permissible Drainage Fixture Unit (DFU) loads for sanitary piping can be estimated with the table below.
| Maximum Drainage Fixture Units (DFU) | |||||
| Pipe Size | Horizontal fixture branch | Stacks less than 3 stories in height | Stacks more than 3 stories high | ||
| NPS (inches) | DN (mm) | ||||
| Total for stack | Total for one story | ||||
| 1 1/20) | 40 | 3 | 4 | 8 | 2 |
| 20) | 50 | 6 | 10 | 24 | 6 |
| 2 1/20) | 65 | 12 | 20 | 42 | 9 |
| 3 | 80 | 201) | 481) | 722) | 201) |
| 4 | 100 | 160 | 240 | 500 | 90 |
| 5 | 125 | 360 | 540 | 1100 | 200 |
| 6 | 150 | 620 | 960 | 1900 | 350 |
0) No water closet permitted
1) Maximum two water closets
2) Maximum six water closets
| Maximum Drainage Fixture Units (DFU) | |||
| Pipe Size | Slope in/ft (cm/m) | ||
| NPS (inches) | DN (mm) | ||
| 1/4 (2.1) | 1/2 (4.2) | ||
| 20) | 50 | 21 | 26 |
| 2 1/20) | 65 | 24 | 31 |
| 3 | 80 | 421) | 501) |
| 4 | 100 | 216 | 250 |
| 5 | 125 | 480 | 575 |
| 6 | 150 | 840 | 1000 |