A boiler is used for generating steam. It does this by heating water to its boiling point, after which steam will evaporate from it. When you boil a kettle of water, you will shut off the fire or electric power when the water comes to a boil.As more and more steam is evaporated, the water becomes more and more concentrated with salts and other impurities. If you use your kettle for a long while, you will see some chalky deposits inside it. The fresh water supplied to replenish those lost through evaporation cannot be pure and free from salts.

A boiler is used for generating steam. It does this by heating water to its boiling point, after which steam will evaporate from it. When you boil a kettle of water, you will shut off the fire or electric power when the water comes to a boil.As more and more steam is evaporated, the water becomes more and more concentrated with salts and other impurities. If you use your kettle for a long while, you will see some chalky deposits inside it. The fresh water supplied to replenish those lost through evaporation cannot be pure and free from salts.