Water hardness refers to the concentration of specific minerals dissolved in water, primarily calcium and magnesium.
Understanding Water Hardness
Based on available information, water hardness or hardness in water is a measure of the amount of calcium and magnesium in the water. The more calcium and magnesium the water contains, the harder the water. These minerals are picked up as water flows through soil and rocks containing them, such as limestone.
The level of hardness is typically quantified in specific units. Water hardness is usually expressed in milligrams per litre (mg/L) or in ppm (parts per million), which are equivalent units (1 mg/L = 1 ppm).
How Water Hardness is Classified
Water hardness is classified into different categories based on the total concentration of calcium and magnesium ions (usually expressed as the equivalent amount of calcium carbonate, CaCO₃). While there isn't one single universally mandated classification scale, common standards exist to categorize water as soft, moderately hard, hard, or very hard.
Here is a widely used classification scale:
| Classification | Hardness Range (mg/L or ppm as CaCO₃) |
|---|---|
| Soft Water | 0 - 60 |
| Moderately Hard | 61 - 120 |
| Hard Water | 121 - 180 |
| Very Hard Water | Over 180 |
- Soft Water: Contains low concentrations of dissolved minerals. It lathers easily with soap.
- Moderately Hard Water: Contains a moderate amount of minerals. Lathering is still relatively easy.
- Hard Water: Contains significant levels of minerals. Can make it difficult to form a lather with soap and may lead to scale buildup.
- Very Hard Water: High mineral content, causing notable soap scum and scale issues.
This classification helps determine potential effects of the water on household appliances, pipes, and its interaction with soap and detergents.
