Yes, calcium chloride absolutely makes water hard.
Understanding why requires looking at what causes water hardness in the first place. Water hardness is primarily determined by the concentration of dissolved minerals, specifically multivalent cations. The most common of these are calcium (Ca²⁺) and magnesium (Mg²⁺) ions.
Why Calcium Chloride Contributes to Hardness
Based on the provided information, Yes, Calcium Chloride will cause hardness in water. This is because all water soluble salts of calcium are known to contribute to water hardness. When calcium chloride (CaCl₂) dissolves in water, it dissociates into calcium ions (Ca²⁺) and chloride ions (Cl⁻).
Since calcium ions (Ca²⁺) are multivalent cations, their presence significantly increases the total hardness of the water. The more calcium chloride dissolved, the harder the water becomes.
What is Water Hardness?
Water hardness is typically measured in units such as milligrams per liter (mg/L) or parts per million (ppm) of calcium carbonate (CaCO₃) equivalents. It is categorized based on the concentration of these dissolved minerals:
- Soft Water: Less than 60 mg/L CaCO₃
- Moderately Hard Water: 60-120 mg/L CaCO₃
- Hard Water: 120-180 mg/L CaCO₃
- Very Hard Water: Greater than 180 mg/L CaCO₃
Adding calcium chloride directly increases the concentration of calcium ions, thereby increasing the water's hardness level.
Practical Implications of Hard Water
Increasing water hardness, whether naturally occurring or due to added compounds like calcium chloride, can have several practical effects:
- Soap Scum: Hard water reacts with soap to form insoluble soap scum, making it less effective for cleaning and leaving residue on surfaces and fabrics.
- Scale Buildup: Heating hard water can cause the calcium ions to precipitate out as calcium carbonate scale (limescale), which can clog pipes, reduce efficiency in water heaters and appliances, and shorten their lifespan.
- Taste and Feel: Some people notice a difference in the taste of hard water, and it can leave skin and hair feeling dry or sticky after washing.
Adding calcium chloride is sometimes done intentionally for specific purposes, such as in swimming pools to maintain calcium balance and prevent plaster erosion, or in brewing water to adjust mineral profiles. In these contexts, the resulting increase in hardness is a known and desired effect.
Therefore, any addition of a water-soluble calcium salt like calcium chloride will indeed contribute to the water's hardness.
