| 83.2 mg/l as calcium = 208 mg/l as calcium carbonate |
|
Classification of water hardness |
| The amount of hardness is sometimes expressed by descriptive words. The following table shows how these descriptions may be related to the numerical value of the hardness in common units. |
|
Description |
Hardness in mg/l as calcium |
Hardness in mg/l as calcium carbonate |
| Soft |
0 - 20 |
0 - 50 |
| Moderately soft |
20 - 40 |
50 - 100 |
| Slightly hard |
40 - 60 |
100 - 150 |
| Moderately hard |
60 - 80 |
150 - 200 |
| Hard |
80 - 120 |
200 - 300 |
| Very Hard |
over 120 |
over 300 |
|
(mg/l = milligrammes per litre = 1 part per million) |