The terms “distilled” versus “vapor distilled” on bottled water labels often confuse consumers seeking highly purified water. Both refer to water purified by removing impurities, but the linguistic difference suggests a variation in method or quality. Understanding the science behind distillation and the commercial use of these terms is important for making an informed choice.
Understanding Standard Distillation
Standard distillation is a purification method that mimics the natural hydrologic cycle. The raw source water is first heated to its boiling point, converting the liquid into steam or vapor. This vaporization leaves behind nearly all non-volatile contaminants, such as heavy minerals, salts, and total dissolved solids (TDS).
The purified steam is then routed into a separate, cooler chamber where it condenses back into a liquid state. This collected liquid is defined as distilled water, characterized by its low concentration of impurities. The process effectively removes inorganic substances, bacteria, and viruses because these contaminants do not vaporize.
The Characteristics of Vapor Distillation
The term “vapor distillation” is frequently used commercially to describe standard distillation that includes additional purification stages. This label serves as a marketing differentiator, implying a higher level of purity. The initial step is identical: heating water to create pure vapor and then condensing it back into a liquid.
However, commercial operations often follow this initial distillation with subsequent steps like carbon filtration or deionization. Activated carbon filtration is effective at removing volatile organic compounds (VOCs) that may have carried over with the steam. Some manufacturers may also employ multiple distillation passes or superheat the vapor before condensation. These extra steps are what the “vapor distilled” label often signifies, suggesting a multi-barrier approach to purification.
Direct Comparison: Are They the Same?
Scientifically, “distilled water” and “vapor distilled water” describe the same end product: water purified by being turned into steam and then condensed. The scientific definition of distillation inherently involves creating water vapor, meaning all distilled water is technically “vapor distilled.” The difference lies primarily in commercial labeling and the implied post-distillation treatment.
When a bottle is labeled simply “distilled water,” it confirms the fundamental purification process of boiling and condensation has occurred. A product labeled “vapor distilled” usually signals that the manufacturer implemented extra filtration steps, such as carbon filters or deionization resins. These additional steps polish the water further, potentially removing trace VOCs or contaminants that a single distillation might miss. For the consumer, this suggests a slightly greater assurance of purity due to the multi-stage refinement.
Practical Applications for Distilled Water
The applications for distilled water are driven by its lack of total dissolved solids, which prevents mineral buildup. For medical equipment like Continuous Positive Airway Pressure (CPAP) machines, distilled water prevents mineral deposits from damaging the heating element. In household appliances such as steam irons and humidifiers, the absence of minerals prevents limescale accumulation, extending the device’s lifespan.
Distilled water is also used in automotive applications, particularly in lead-acid batteries and cooling systems, where mineral-free water avoids corrosion and scale formation. In laboratories, high purity is required for preparing solutions and calibrating sensitive equipment. For these practical uses, the distinction between “distilled” and “vapor distilled” is negligible, as both processes effectively remove dissolved solids.