The common belief that simply boiling water transforms it into distilled water is a widespread misconception. While boiling is an effective method for making water safer to drink, it achieves a different result from distillation. Water is not just pure H₂O, but a solution containing dissolved minerals, salts, and sometimes biological or chemical contaminants. Understanding the physical changes that occur when heat is applied reveals why boiling and distillation serve distinct purposes in treating water.
The Science of Boiling Water
When water reaches its boiling point of 100°C (212°F) at sea level, the intense heat serves a sanitation function. This temperature is sufficient to kill almost all pathogenic microorganisms, including bacteria, viruses, and parasites. Boiling does not physically remove impurities; it only sterilizes the water. As pure water molecules turn to steam and escape, non-volatile substances remain behind, increasing the concentration of total dissolved solids (TDS), such as salts and heavy metals. While the boiled water is free of living microbes, it may have a higher concentration of chemical contaminants.
Defining Distillation and Purification
Distillation is a physical separation process that mimics the natural hydrologic cycle of evaporation and condensation. This method relies on the difference between the boiling point of water and that of most contaminants. The process begins by heating the source water until it vaporizes into steam, leaving behind the majority of non-volatile impurities. The resulting water vapor is nearly pure H₂O, which is then directed into a separate, cooled chamber where it undergoes condensation and reverts back to its liquid state. The collected liquid—the distillate—is water physically separated from almost all minerals, salts, heavy metals, and many contaminants.
Comparing Purity: Boiling vs. Distillation
The difference between boiled water and distilled water is defined by the extent of purification achieved. Boiling is fundamentally a sanitation method focused on destroying biological hazards, but the resulting water still contains the original Total Dissolved Solids (TDS). Distillation, conversely, is a comprehensive purification method that physically strips the water of its dissolved materials. Standard tap water often has a TDS content ranging from 100 to 400 parts-per-million (PPM), which boiled water retains. Properly distilled water is one of the purest forms available, possessing an extremely low TDS count, often between 1 and 5 PPM. This purity is why distilled water is used in laboratories and appliances where mineral buildup is a concern.
Simple Steps for Homemade Distilled Water
Distillation can be performed relatively simply at home using a large pot, a heat-safe collection vessel, the pot’s lid, and ice.
The Distillation Process
- Fill the large pot with water and place the smaller, empty collection bowl inside so it rests on a rack above the bottom, ensuring it will not touch the boiling water.
- Place the pot lid upside down on the large pot, and then put ice on top of the inverted lid to create a cold surface.
- Heat the water to create steam, which will rise and immediately hit the cold, inverted lid.
- The rapid cooling causes the steam to condense into pure water droplets, which drip down the lid’s curve and into the collection bowl.
- Maintain a steady simmer rather than a vigorous boil to prevent splashing the source water into the collection bowl.
- Once the process is complete, carefully remove the hot collection bowl containing the distilled water.