What happens to water when it is reboiled?

Every day most of us start with a cup of coffee or tea. Often, water left in the kettle from the evening is used to prepare drinks. A question arises: how safe is it to boil water twice or more?

During the first boiling, a significant amount of oxygen evaporates from the water. Reboiling does not significantly change this indicator. Also, with repeated heating, the concentration of minerals and salts in the water increases slightly.

However, these changes become problematic only in the case of multiple boiling of a large volume of water. If you just boiled the kettle twice for your morning drink, it does not pose a significant health risk.

Scientific data confirms the safety of this practice. According to a study published in The Journal of Water and Health in 2020 (article "Effects of multiple boiling on water quality: a laboratory study"), even after several boiling cycles, the concentration of magnesium and calcium in water does not exceed safe levels.