Code | Class | Value |
1 | Rapid drainage | >60 mm/h |
2 | Moderate to rapid drainage | 20 - 60 mm/h |
3 | Moderate drainage | 5 - 20 mm/h |
4 | Slow to moderate drainage | 2 - 5 mm/h |
5 | Slow drainage | 1 - 2 mm/h |
6 | Very slow drainage | <1 mm/h |