Distilled water

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Bottle for distilled water in the Real Farmacia in Madrid.

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.


Drinking water has been distilled from sea water since at least ca. 200 AD when the process was clearly described by Alexander of Aphrodisias.[1] Its history predates this, as a passage in Aristotle's Meteorologica (II.3, 358b16) refers to the distillation of water.[2] Captain Israel Williams of the Friendship (1797) improvised a way to distill water, which he described in his journal.[3]


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.[4]

Distilled water is also preferable to tap water for use in model steam engine boilers and model engines of other types.[citation needed] 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.

A boiling water distiller. Boiling tank on top and holding tank on the bottom.

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.[5]

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.[6]

Another application is to increase the density of the air to assist early airplane jet engines during takeoff in "hot and high" atmospheric conditions, as was used on the early Boeing 707.[7]

Distilled water is also used in Constant Positive Airway Pressure (CPAP) machines. These machines help people with sleep apnea breathe throughout their sleep cycles. The water is used to humidify the air entering the user's nasal cavity, mouth, and throat. Distilled water will not leave any contaminants behind when the humidifier in the CPAP machine evaporates the water.[8][9]

Use in steam irons[edit]

Although possibly once the recommended procedure, using distilled water in steam irons for pressing clothes (once thought to help reduce mineral build-up and increase iron life),[10] now most manufacturers say that distilled water is not only no longer necessary in their irons, but can actually result in malfunction, including spitting and leaking during use. This may occur due to the lack of impurities in distilled water, which can heat beyond the normal boiling point, rather than nucleating around dissolved impurities at the normal boiling point and producing the necessary steam when it hits the soleplate. It has been suggested that this superheated (distilled) water in an iron will flash boil when disturbed (as with moving an iron), and cause the iron to spit, leak, and possibly scald the user.

Equipment to distill water[edit]

Typical laboratory distillation unit

Up until World War II, distilling sea water to 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 the compression still, that 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 gallons of fresh water could be extracted from sea water for every gallon of fuel used. During World War II this unit became standard on Allied ships and on trailer mounts for armies. This method was in widespread use for ships and portable water distilling units[11] during the latter half of the century. Modern vessels now use flash-type evaporators to boil sea water, heating the water to between 70-80 °C and evaporating the water in a vacuum - this is then collected as condensation before being stored.

Solar stills can be relatively simple to design and build, with very cheap materials.[12]

Drinking distilled water[edit]

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.[13][14] Some other components such as trace levels of aluminium 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.[15]

Distilled water is also used for drinking water in arid seaside areas lacking sufficient freshwater, via desalination of seawater.[16]

Health effects[edit]

Long-term consumption of distilled or demineralized water, containing low TDS levels, is not recommended and can be linked to increased diuresis, body water volume, and serum sodium concentrations, decreased serum potassium concentration, and increased elimination of sodium, potassium, chloride, calcium and magnesium ions from the body. [16]

See also[edit]


  1. ^ Taylor, F. Sherwood (1945). "The Evolution of the Still". Annals of Science 5 (3): 186. doi:10.1080/00033794500201451. ISSN 0003-3790. 
  2. ^ Aristotle. "Meteorology – Book II" (PDF). The University of Adelaide. Retrieved 2010-06-14. 
  3. ^ Trow, Charles Edward. "Chapter XVI". The old shipmasters of Salem. New York and London: G.P. Putnam's Sons. pp. 178ff. OCLC 4669778. Short of Fresh Water Causes Alarm — Captain Williams's Invention to Make Salt Water Fresh — His 'Still' Described by him 
  4. ^ [1]
  5. ^ [2]
  6. ^ "How to Brew - By John Palmer - Reading a Water Report". howtobrew.com. 
  7. ^ Down the Susquehanna to the Chesapeake By John H. Brubaker, Jack Brubaker page 163
  8. ^ "Distilled Water And CPAP Usage". cpap.com. 
  9. ^ http://www.cpap.com/cpap-faq/Humidifiers.html#why-do-i-need-to-use-distilled-water-with-in-my-humidifier-chamber
  10. ^ "Steam Iron Buying Guide". homeinstitute.com. 
  11. ^ "Popular Science". 
  12. ^ http://www.thefarm.org/charities/i4at/surv/sstill.htm
  13. ^ "Drinking Water Contaminants". water.epa.gov. 2011. Retrieved October 25, 2011. 
  14. ^ "EWG's Drinking Water Quality Analysis and Tap Water Database | Environmental Working Group". ewg.org. 2011. Retrieved October 25, 2011. 
  15. ^ Anjaneyulu, L.; Kumar, E. Arun; Sankannavar, Ravi; Rao, K. Kesava (13 June 2012). "Defluoridation of Drinking Water and Rainwater Harvesting Using a Solar Still". Industrial & Engineering Chemistry Research 51 (23): 8040–8048. doi:10.1021/ie201692q. 
  16. ^ a b Kozisek, F (2005). "Health risks from drinking demineralised water (application/pdf Object)". who.int. Retrieved October 25, 2011.  (Chapter 12 of the World Health Organization report Nutrients in drinking-water)