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In watts
| Nominal pipe size | Dry main with gradient | |||||
|---|---|---|---|---|---|---|
| in | mm | Wet main | 1 in 200 | 1 in 600 | Vertical | Vent pipes |
| 1/2 | 15 | 30,000 | 10,000 | 6,000 | 10,000 | 12,000 |
| 3/4 | 20 | 70,000 | 30,000 | 18,000 | 30,000 | 47,000 |
| 1 | 25 | 120,000 | 50,000 | 34,000 | 50,000 | 94,000 |
| 1 1/4 | 32 | 300,000 | 120,000 | 80,000 | 120,000 | 211,000 |
| 1 1/2 | 40 | 420,000 | 176,000 | 117,000 | 176,000 | 293,000 |
| 2 | 50 | 760,000 | 350,000 | 225,000 | 350,000 | 530,000 |
| 2 1/2 | 65 | 1,900,000 | 800,000 | 510,000 | 800,000 | 1,200,000 |
| 3 | 80 | 2,700,000 | 1,200,000 | 740,000 | 1,200,000 | 1,870,000 |
In Btu/hr
| Nominal pipe size | Dry main with gradient | |||||
|---|---|---|---|---|---|---|
| in | mm | Wet main | 3/16 in per yd | 1/16 in per yd | Vertical | Vent pipes |
| 1/2 | 15 | 100,000 | 40,000 | 24,000 | 40,000 | 40,000 |
| 3/4 | 20 | 240,000 | 108,000 | 68,000 | 108,000 | 160,000 |
| 1 | 25 | 400,000 | 192,000 | 120,000 | 192,000 | 320,000 |
| 1 1/4 | 32 | 1,000,000 | 440,000 | 280,000 | 440,000 | 720,000 |
| 1 1/2 | 40 | 1,440,000 | 600,000 | 400,000 | 600,000 | 1,000,000 |
| 2 | 50 | 2,600,000 | 1,120,000 | 700,000 | 1,120,000 | 1,800,000 |
| 2 1/2 | 65 | 6,400,000 | 2,800,000 | 1,760,000 | 2,800,000 | 4,000,000 |
| 3 | 80 | 9,600,000 | 4,000,000 | 2,520,000 | 4,000,000 | 6,400,000 |