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