Hardness of Water

Hardness:- It shows the amount of multivalent ions mostly comprised of Calcium and Magnesium dissolve in water.

Definition:- Property of water by which it does not produce lather when reacting with soap.

Hard water contains a high amount of Calcium, Magnesium (Chloride, sulfate, carbonate, and bicarbonate) or any other metal iron. Whereas Soft water contains very less or Nill amount of this salt.

Soft Water

0-50 mg/L

Modratory  Hard Water

50-150 mg/L

Hard water

150-300 mg/L

Very Hard water

>300 mg/L


Type Of Hardness:-

Temporary Hardness: Due to Bicarbonate ions, which can be removed by Boiling.(carbonate)

Permanent Hardness: Due to Sulphate ions, which cannot be removed by Boiling.(non-carbonate)


Calcium and Magnesium, the two principal ions, are present in many rocks. The Main source of Hardness are  limestone and chalk. Other sources include rocks, seepages and soils. They are also common essential mineral constituents of food. The little contribution to the hardness of water is also made by other polyvalent ions, such as Aluminum, Barium, Iron, Manganese, Strontium and Zinc.

Damage due to hardness

  • Scaling in Membrane system-RO, Nanofiltration, Ultrafiltration, Microfiltration

  • Scaling in the Thermal system- Boiler, Evaporator, Heat Exchanger.

  • Scaling in Cooling tower, Cooling line.

  • Scaling in Faucetware, Bathroom.

  • Scaling effect overall efficiency of system.

  • When you take potentially very hard water for a longer time then it will affect the absorption of important minerals.


We can Measure Hardness by titration or with the Help by Machine.


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