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Theory:

The following methods are used to remove water hardness depending on whether the hardness is temporary or permanent.
  • Boiling
  • Clark’s method
  • Adding washing soda
  • Ion-exchange
  • Distillation
Boiling
 
Boiling may easily remove temporary hardness from water. When calcium hydrogen carbonate is heated, it decomposes into insoluble calcium carbonate. After that, the insoluble carbonates are filtered out of the water. This softens the hard water and makes it suitable for usage.
 
Clark’s method

Calcium hydroxide is used as a reagent in Clark’s method. It removes the hardness of water by converting bicarbonates into carbonate.
 
Adding washing soda

Washing soda is used to remove the water's permanent hardness. Chlorides and sulphates are converted to insoluble carbonates when washing soda is added. Filtration is used to remove the insoluble carbonates.
 
Ion-exchange
 
Passing water through a column of ion-exchange resins, calcium and magnesium ions are replaced by sodium ions. This is another way to eliminate hardness. This converts hard water into soft water.
 
Distillation

Distillation can be used to eliminate both temporary and permanent hardness. Distilled water is the water obtained after distillation. It is the purest form of drink water.
Water that has been distilled or boiled has no taste. The presence of dissolved substances such as air, carbon dioxide and minerals give drinking water a pleasant taste.