Distilled water is water that has been boiled into vapour and condensed back into liquid in a separate container. Impurities in the original water that do not boil below or near the boiling point of water remain in the original container. Thus, distilled water is a type of purified water.
In this blog, Pritish Kumar, discusses Distilled water, its applications, types of equipment to distil water and the health effects caused by it.
In chemical and biological laboratories, as well as in industry, in some appliances, deionized water can be used instead of distilled water as a cheaper alternative. If exceptionally high-purity water is required, double distilled water is used.
In general, non-purified water could cause or interfere with chemical reactions as well as leave mineral deposits after boiling away. One method of removing impurities from water and other fluids is distillation.
Equipment to distill water
Until World War II, distilling sea water to produce fresh water was time-consuming and expensive in fuel. The saying was: “It takes one gallon of fuel to make one gallon of fresh water.” Shortly before the war, Dr. R. V. Kleinschmidt developed a compression still, which became known as the Kleinschmidt still, for extracting fresh water from sea water or contaminated water. By compressing the steam produced by boiling water, 175 US gal (660 l; 146 imp gal) of fresh water could be extracted from sea water for every gallon (3.8 l; 0.83 imp gal) of fuel used.
During World War II this equipment became standard on Allied ships and on trailer mounts for armies. This method was in widespread use in ships and portable water distilling units. During the latter half of the century. Modern vessels now use flash-type evaporators to boil sea water, heating the water to between 70 and 80 °C (158 and 176 °F) and evaporating the water in a vacuum; this is then collected as condensation before being stored.
Drinking distilled water
Bottled distilled water can usually be found in supermarkets or pharmacies, and home water distillers are available as well. Water purification, such as distillation, is especially important in regions where water resources or tap water is not suitable for ingesting without boiling or chemical treatment.
Municipal water supplies almost always contain trace components at levels which are regulated to be safe for consumption. Some other components such as trace levels of aluminum may result from the treatment process (see water purification). Fluoride and other ions are not removed through conventional water filter treatments. However, distillation eliminates most impurities.
Distilled water is also used for drinking water in arid seaside areas lacking sufficient freshwater, via desalination of seawater.
Distillation removes all minerals from water. This results in demineralised water, which has not been proven to be healthier than drinking water. The World Health Organization investigated the health effects of demineralised water in 1982, and its experiments in humans found that demineralised water increased diuresis and the elimination of electrolytes, with decreased serum potassium concentration.  Magnesium, calcium, and other nutrients in water can help to protect against nutritional deficiency.
The drinking of distilled water as a replacement for drinking water has been both advocated and discouraged for health reasons. Distilled water lacks minerals and ions such as calcium that play key roles in biological functions such as in nervous system homeostasis, and are normally found in potable water. The lack of naturally occurring minerals in distilled water has raised some concerns.