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C 304.2 Size of Building Drain and Building Sewer
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The maximum number of drainage fixture units allowed on the building drain or building sewer of a given size shall be in accordance with Table C 304.2. The size of a building drain or building sewer serving a water closet shall be not less than 3 inches (80 mm).
| DIAMETER OF PIPE (inches) |
MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS FOR SANITARY BUILDING DRAINS AND RUNOUTS FROM STACKS | |||
|---|---|---|---|---|
| SLOPE (inches per foot) | ||||
| 1/16 | 1/8 | 1/4 | 1/2 | |
| 2 | — | — | 21 | 26 |
| 21/2 | — | — | 24 | 31 |
| 3 | — | 20 | 422 | 502 |
| 4 | — | 180 | 216 | 250 |
| 5 | — | 390 | 480 | 575 |
| 6 | — | 700 | 840 | 1000 |
| 8 | 1400 | 1600 | 1920 | 2300 |
| 10 | 2500 | 2900 | 3500 | 4200 |
| 12 | 3900 | 4600 | 5600 | 6700 |
| 15 | 7000 | 8300 | 10 000 | 12 000 |
For SI units: 1 inch = 25 mm, 1 inch per foot = 83.3 mm/m
Notes:
1 On-site sewers that serve more than one building shall be permitted to be sized according to the current standards and specifications of the administrative authority for public sewers.
2 A maximum of two water closets or two bathroom groups, except in single-family dwellings, where a maximum of three water closets or three bathroom groups shall be permitted to be installed.
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