Ions can be removed from water, typically through a chemical process. An ion is an atom or molecule with an abnormal number of electrons. While there are some scientific applications for deionised water, there are not very many household applications for it. However, some individuals find uses for it at home. Homemade deionised water can be achieved with some tools and some basic knowledge.
Kits designed to deionise water for home use can be purchased online or in some scientific supply stores. These kits generally remove divalent cations (atoms or radicals with two additional electrons, frequently present in hard water) with sodium ions in order to create "soft" water. This is somewhat different than a scientific kit, which removes both cations (particles with a positive charge) and anions (particles with a negative charge) such as hydrogen and hydroxyl for medical or scientific purposes.
Deionised water can be used around the house for various tasks. Since the ions have been removed, there are no minerals left in the water to create a residue, making it useful for use in steam irons, window cleaning or even car washing. Deionised water can also be used in conjunction with clarifying shampoos to help remove residue and other impurities from the hair.
While there may be some benefits to using deionised water for cleaning or housekeeping projects, it should generally not be used for drinking. According to the World Health Organization, deionised water offers little to no benefit for drinking, due to the lack of calcium, magnesium or other essential elements normally contained in water. In addition, the water will probably have a poor taste and will not satisfy thirst.
Consumption of deionised water, either through cooking or drinking, may result in negative effects on metabolism or may also result in the elimination of important nutrients from the body, including sodium, chloride, potassium, calcium and magnesium. In addition, food that is prepared with deionised water may lose almost all essential elements, which can have a health effect over time.