Water hardness table
Level
Type
Water hardness
°dH
°T.H.
mmol/l
Clarke
1
soft
0-7
0-15
0-1.5
0-9
2
medium
8-14
16-25
1.6-2.5
10-16
3
hard
15-21
26-37
2.6-3.7
17-25
4
very hard
> 21
> 37
>3.7
>25
ENGLISH
21
