No, boiled water is not considered distilled water, despite both processes utilizing heat to treat water. While boiling and distillation share an initial heating step, the final product’s purity differs significantly based on how the water is collected. Boiling is a process of thermal disinfection, which kills impurities. Distillation is a comprehensive physical separation technique that physically separates impurities from the water molecules. The resulting liquid from each process is used for different purposes based on its final composition.
Boiling: A Method of Disinfection
Boiling water is a long-established method for making microbiologically unsafe water safe to drink. Heating water to its boiling point of 212°F (100°C) for a minimum of one minute effectively inactivates waterborne pathogens, including bacteria, viruses, and protozoan cysts like Giardia and Cryptosporidium. The heat causes structural damage to the microorganisms, eliminating the risk of waterborne illness. Boiling can also cause some volatile organic compounds (VOCs), such as chlorine, to evaporate.
However, non-volatile impurities are not removed by this process. Substances like inorganic salts, heavy metals, and minerals have boiling points much higher than water. As the pure water evaporates as steam, these contaminants remain in the vessel, becoming more concentrated in the reduced volume of liquid left behind. If water contains lead, boiling will actually increase the concentration of lead in the remaining water.
Distillation: Separation by Phase Change
Distillation separates water from its dissolved impurities through a phase change cycle. The process begins by heating the source water until it vaporizes into steam. This steam consists of pure water molecules (H₂O) that leave all non-volatile substances behind in the boiling chamber.
The pure water vapor is then channeled away from the boiling vessel and cooled in a separate condenser. As the steam cools, it condenses back into its liquid state. This collected liquid is the finished distilled water, which is free from the majority of contaminants because they never vaporized.
Why Boiled Water is Not Pure Water
Boiled water contains a higher concentration of non-volatile dissolved solids than the original source water. When water is boiled, common minerals like calcium and magnesium are left behind, often forming a visible, chalky white residue or scale on the bottom of the pot. Distillation, in contrast, removes up to 99.5 percent of impurities, including hardness minerals, salts, and heavy metals such as lead and arsenic.
This high level of purity dictates the specific applications for distilled water. Industries and laboratories require it because trace amounts of minerals found in boiled water can interfere with chemical reactions or cause equipment failure. Using boiled water in devices like car batteries, medical autoclaves, or humidifiers will lead to mineral scale buildup that can damage the machinery. Boiling is focused on biological safety, while distillation is focused on achieving material purity by physically removing dissolved solids.