Deionized water, also known as demineralized water, Demin water, DI water, or DM water, is water that has had the minerals normally present in water removed. Water out of your tap typically has calcium, sodium, iron, copper, chlorine, magnesium, potassium, and other minerals in it. Deionized water is created by filtering water through resin beads that attract many of the minerals out of the water. This filtering produces softer water that is absent of many minerals normally found in tap water; however, it does not necessarily remove certain organic compounds (like bacteria or viruses) or dissolved solids such as some heavy metals or sugars.

Deionization is just one of the ways water may be purified. Purified water may refer to water that has been filtered using a wide variety of filters, not necessarily just the resin beads used to deionize water. Carbon filters, reverse osmosis, ultraviolet lights, and distillation are all different ways to produce purified water. The type of purified water you need will likely depend on how you intend to use the water.

In This Article

Uses for Deionized Water

Deionized water is used in areas where the normally abundant minerals in water would interfere. Because the minerals present in water leave behind a residue when evaporated, deionized or demineralized water is often used in applications where water is heated and evaporated or when the chemistry of the water is very important.

Home Uses

  • Lead-acid car batteries: Because normal tap water can leave mineral deposits behind and damage the battery, lead-acid batteries should be topped off with demineralized or distilled water.
  • Automobile radiators: Like with lead-acid batteries, if your car radiator needs to be topped off, it is preferable to use deionized or distilled water to prevent mineral buildup in your car’s cooling system.
  • Humidifiers and humidors: These devices continuously evaporate water causing mineral deposits to build up over time and clog or otherwise damage the device. Using deionized or distilled water prevents this buildup.
  • Steam irons and mops: Some steam irons, particularly older models, recommend the use of deionized or distilled water in order to prevent components becoming clogged from mineral deposits.
  • Aquariums: Although fish can’t live in deionized water alone, many aquariums are filled initially with deionized or distilled water and then with appropriate minerals, chemicals, and nutrients introduced to the water to produce a habitable environment.

Industrial Uses

  • Steam boilers and turbines: Because improper water chemistry and contaminants can cause damage, very pure water, such as deionized water, is often used in large steam producing components.
  • Electronic manufacturing: Deionized water has lower conductivity and less impurities, so electronic manufacturers often use it to clean items in the manufacturing process.
  • Cooling systems: Much like a car’s radiator, large scale cooling devices (such as those on laser cutters) require water to help transfer heat away from the device. Deionized water is used in these systems to prevent damage and corrosion of the device from impurities in tap water.

Laboratory Uses

  • Pharmaceutical manufacturing: When water is required to manufacture medicines, supplements, or other items, demineralized or distilled water is often used to ensure the impurities associated with normal tap water are removed.
  • Cosmetic manufacturing: Pure water is very important for manufacturing makeup and lotions in order to ensure the products do not leave traces of minerals or other contaminants behind.
  • Cleaning glassware and instruments: Because deionized water has had most of the minerals removed, it will not leave residue behind on glassware and other instruments.

Where to Buy Deionized Water

Locals Stores

Pure deionized water is more difficult to find than other forms of purified water, such as distilled water, which is available at most grocery stores. For this reason, you may have difficulty finding deionized water at a store near you. Here are a couple locations to start your search:

  • Local specialty water stores: Stores that sell water treatment systems, have water delivery service, or specialize in selling water may be able to service you.
  • Industrial supply stores: Since deionized water is used for many industrial applications, industrial supply stores such as Grainger may sell deionized water.

Online Stores

Purchasing deionized water online will likely be most convenient because it can be difficult to find at nearby stores. Here are a few places to start your search:

  • Amazon: Amazon sells everything including deionized water in plastic containers up to 5 gallons and smaller amounts in glass containers.
  • Chemical supply stores: Sites that supply materials for laboratories typically sell deionized water. For example, Chemworld sells deionized water in various containers with quantities as small as 2 ounces and as large as 275 gallons. The Science Company also sells deionized water in 1 gallon plastic jugs.
  • Electronic supply stores: Sites such as NewEgg sell demineralized water in four liter and ten liter amounts for cleaning electrical components.
  • Industrial supply stores: Even if there isn’t a physical store location near you, Grainger also sells deionized water on its website. Amounts from one liter to 200 liters are available in plastic containers and drums.
  • Walmart: Walmart sells deionized water online from as little as 4 liters in a plastic jug up to 10 liters in boxed plastic.

Water Delivery Companies

  • Culligan: Culligan offers delivery service of deionized water in five gallon plastic containers in many of its service areas. Find a Culligan dealer near you to find out if they deliver demineralized or deionized water in your area.
  • Local water supply stores: Because so many water delivery companies service only small, localized areas, it’s impossible to know which companies may service your area. A quick search online for nearby water stores should point you in the right direction.

 In Summary

Deionized water is useful in many applications because of its purity and lack of minerals. However, since its applications are mostly specific to specialty industries, you may find a hard time finding deionized or demineralized water at a store near you. For many home uses, distilled water, which is widely available in grocery stores and convenience stores, can likely be substituted in place of demineralized water. If you do need deionized water though, purchasing online will likely be most convenient for you.