| Pipe Size | Flow Capacity | Rainfall Intensity (mm/hr) | ||||||||
| 50 | 100 | 150 | 175 | 200 | ||||||
| mm. | inch | L/s | CMH | CFM | GPM | Catchment Area of Roof (m2) | ||||
| 50 | 2 | 1.45 | 5.22 | 3.07 | 23 | 101 | 51 | 34 | 29 | 25 |
| 80 | 3 | 4.22 | 15.19 | 8.95 | 67 | 298 | 149 | 99 | 85 | 74 |
| 100 | 4 | 9.08 | 32.69 | 19.25 | 144 | 643 | 321 | 214 | 184 | 161 |
| 125 | 5 | 16.46 | 59.26 | 34.90 | 261 | 1,165 | 583 | 388 | 333 | 291 |
| 150 | 6 | 26.75 | 96.30 | 56.71 | 424 | 1,895 | 948 | 632 | 541 | 474 |
| 200 | 8 | 57.60 | 207.36 | 122.11 | 913 | 4,082 | 2,467 | 1,360 | 1,166 | 1,020 |
| 250 | 10 | 104.41 | 375.88 | 221.35 | 1,655 | 7,401 | 3,700 | 2,467 | 2,114 | 1,850 |
| 300 | 12 | 169.83 | 611.39 | 360.04 | 2,692 | 12,035 | 6,017 | 4,012 | 3,438 | 3,008 |
| 375 | 15 | 307.87 | 1,108.33 | 652.68 | 4,880 | 21,821 | 10,910 | 7,274 | 6,234 | 5,455 |
Note
a) Flow capacities are based on stacks flowing 7/24 full.
b) Interpolation between rainfall rates is permitted.
Source
National Standard Plumbing Code, 2006, Chapter 13, Table 13.6.1