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| Distilled water |
Distilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.
Fresh water has been distilled from sea water since at least ca. 200 AD when the process was clearly described by Alexander of Aphrodisias. Its history predates this, as a passage in Aristotle's Meteorologica (II.3, 358b16) refers to the distillation of water.
In chemical and biological laboratories, as well as industry, cheaper alternatives such as deionized water are preferred over distilled water. However, if these alternatives are not sufficiently pure, distilled water is used. Where exceptionally high purity water is required, double distilled water is used.
Distilled water is also commonly used to top off lead acid batteries used in cars and trucks. The presence of other ions commonly found in tap water will cause a drastic reduction in an automobile's battery lifespan.
Distilled water is preferable to tap water for use in automotive cooling systems. The minerals and ions typically found in tap water can be corrosive to internal engine components, and can cause a more rapid depletion of the anti-corrosion additives found in most antifreeze formulations.
Distilled water is also preferable to tap water for use in model steam engine boilers and model engines of other types. Mineral build-up resulting from the use of tap water in model boilers can severely reduce the efficiency of the boilers if run for long periods. This build-up is known as boiler scale.
Using distilled water in steam irons for pressing clothes can help reduce mineral build-up and make the iron last longer. However, many iron manufacturers say that distilled water is no longer necessary in their irons.
Some people use distilled water for household aquariums because it lacks the chemicals found in tap water supplies. It is important to supplement distilled water when using it for fishkeeping; it is too pure to sustain proper chemistry to support an aquarium ecosystem.
Distilled water is also an essential component for use in cigar humidors. Mineral build-up resulting from the use of tap water (including bottled water) will reduce the effectiveness of the humidor.
In addition, some home brewers, who are interested in brewing a Traditional European Pilsner, will dilute their hard water with distilled water so as to mimic the soft waters of Pilsen.
Another application is to cool off airplane engines during takeoff, as was used on the early Boeing 707.
Distilled water is also used in Constant Positive Airway Pressure (CPAP) machines. These machines are used by people with sleep apnea to help breathing throughout sleep cycles. The water evaporates and is used to humidify the air going in to the users mouth. Distilled water will not leave any contaminants behind when the humidifier in the CPAP machine evaporates the water.