The water we pour into our kettle or pot from the tap contains both useful and harmful elements. On the one hand, it contains important substances such as calcium and magnesium, oxygen and carbon dioxide. On the other hand, it contains dangerous substances such as uranium, barium, chlorine, fluorine and nitrates.

The advantage of boiling is that it destroys some harmful bacteria and also makes the water softer. If you boil water for 15 minutes with steam, the harmful chemical compounds will disappear. But along with these elements, the concentration of calcium and other useful minerals decreases. In this case, chlorine and non-volatile substances remain in the composition and turn into more dangerous carcinogens.

The longer you boil the water, the more nutrients are removed and the more 'useless' it becomes. In addition, after boiling, salt deposits and stains remain on the kettle or the walls of the pot forming a scale. 

If you use an electric kettle, it goes out quickly and the boiling time is short. Therefore, repeated boiling may not be harmful. However, many experts still do not recommend repeating this process and consider it excessive. 

Note that the danger lies not so much in the number of boils, but also in the duration of the process. The longer the water is boiled, the more active the production of negative and harmful substances.

With prolonged and repeated boiling, the hydrogen isotope is precipitated and deuterium is formed. It disrupts the metabolism of materials in the body and prevents the absorption of vitamins. This is a scientific fact that explains why you cannot boil water twice. 

In addition, boiled water tastes unpleasant and with each new boil, it gets worse. The reason for this process is that harmful impurities in the composition of water at a temperature of 100 degrees enter into reactions and become active, resulting in an unpleasant taste. 

Finally, organic substances such as fats, proteins and carbohydrates present in our food react with the residual chlorine to create organochlorine toxic derivatives which are a health hazard.

So, for those who already have a water purification system cook only with it and those who don't seriously consider installing one!