Does boiling water make it safe to drink?

Boiling water makes it safer to drink, but it does not eliminate all potential contaminants. When water reaches its boiling point of 100 °C (212 °F), the intense heat destroys many harmful microorganisms, including bacteria, viruses, and parasites. This is why boiling water for at least one minute (longer at high elevations) is widely recommended as a reliable method for preventing waterborne diseases and parasitic infections such as fasciolopsiasis.

However, boiling water does not remove chemical contaminants such as heavy metals (including lead), pesticides, or other pollutants. Natural spring water, once considered clean, has been found contaminated with surface runoff, which boiling alone cannot neutralize. Therefore, although boiling water is effective against biological threats, it is not a comprehensive solution for all types of water contamination.

Boiling can also affect the mineral content of water, especially when it comes to hard water, which contains high levels of calcium and magnesium. When water is boiled, these minerals can precipitate out as insoluble carbonates (such as limescale), reducing hardness. This process, known as temporary hardness removal, can change the mineral content of the water but does not remove all dissolved salts. Importantly, it does not make the water safer to drink if chemical contaminants are present.