The maximum number of drainage fixture units allowed on a
horizontal branch or vertical soil or waste stack of a given
size shall be in accordance with Table C304.3. Stacks shall
be sized based on the total accumulated connected load at
each story or branch interval.
For SI units: 1 inch = 25 mm.
Notes:
| DIAMETER OF PIPE (inches) |
MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS | |||
| HORIZONTAL FIXTURE BRANCH1 |
ONE STACK OF THREE OR FEWER BRANCH INTERVALS |
STACKS WITH MORE THAN THREE BRANCH INTERVALS | ||
| TOTAL FOR STACK | TOTAL AT ONE BRANCH INTERVAL |
|||
| 11/2 | 3 | 4 | 8 | 2 |
| 2 | 6 | 10 | 24 | 6 |
| 21/2 | 12 | 20 | 42 | 9 |
| 3 | 202 | 482 | 722 | 202 |
| 4 | 160 | 240 | 500 | 90 |
| 5 | 360 | 540 | 1100 | 200 |
| 6 | 620 | 960 | 1900 | 350 |
| 8 | 1400 | 2200 | 3600 | 600 |
| 10 | 2500 | 3800 | 5600 | 1000 |
| 12 | 3900 | 6000 | 8400 | 1500 |
| 15 | 7000 | 6000 | 8400 | 1500 |
Notes:
- 1 Does not include branches of the building drain.
- 2 A maximum of two water closets or bathroom groups within each branch interval or more than six water closets or bathroom groups on the stack.
Horizontal
stack offsets shall be sized in accordance with Table C304.2 as required for building drains.
Vertical stack offsets
shall be sized in accordance with Table C304.3 as
required for stacks.