Deionized water is purified water that has been filtered through resin beads to remove some common minerals like calcium, chlorine, and potassium.
It is softer than tap water and is used in applications where water of specific chemistry is required, such as in humidifiers (where mineral deposits could build up) and cooling systems.
Below, we have all of the details of how deionized water can be used and where to buy it.
Where to Buy Deionized Water
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 few places to start your search:
- Aquarium/pet stores: As noted above, deionized water is sometimes used in aquariums, so deionized water and deionization systems can often be found at pet stores that sell or specialize in fish tanks and aquatic supplies. If you are going to use deionized water regularly, buying a deionization system from a store like Fish Doctors in Ypsilanti and Canton, MI can save you money in the long-run.
- 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. If you need a large amount of deionized water, a company like Total Water (which serves Illinois, Indiana, Iowa, Michigan, Minnesota, and Wisconsin) can help you find a filtration system to meet your needs or point you in the right direction to buy smaller quantities.
- Industrial supply stores: Since deionized water is used for many industrial applications, industrial supply stores such as Grainger may sell deionized water.
- Whole Foods Market: Whole Foods sells deionized water, but with electrolytes added. It can be found labeled as “Electrolyte Water” from the store’s 365 Everyday Value brand, but you should check with your local Whole Foods store for pricing and current availability.
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 five 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 two ounces and as large as 275 gallons. The Science Company also sells deionized water in one-gallon plastic jugs.
- Electronic supply stores: Sites such as NewEgg sell demineralized water in four-liter and 10-liter amounts for cleaning electrical components.
- Essential Wholesale & Labs: This retailer of bulk cosmetic ingredients sells deionized water in one-gallon, five-gallon, and 55-gallon quantities.
- 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 four liters in a plastic jug up to 10 liters in boxed plastic.
- Water purification companies: Water treatment companies sell filtration systems and, sometimes, deionized water online. Serv-A-Pure is one company that sells deionized water online in several different sizes, ranging from a single gallon in a plastic jug to a 330-gallon tote.
Water Delivery Companies
- Besco Water Treatment, Inc.: For commercial applications, Besco offers a deionized water delivery service in bulk quantities and accepts tank exchanges. Besco primarily serves Indiana, Michigan, and Ohio.
- Culligan: Culligan offers delivery service of deionized water in five-gallon plastic containers in many of its service areas. Find a Culligan dealer to find out if they deliver demineralized or deionized water in your area.
- Puretec Industrial Water: Puretec delivers portable water tanks and has semitruck water trailers for longer-term deionized water needs. Puretec’s services are available in California, Arizona, Nevada, and New Mexico.
- Local water supply stores: Because so many water delivery companies service only small, localized areas, search for nearby water supply stores using your favorite search engine to find other options in your area.
Uses for Deionized Water
Deionized water — also known as demineralized water, Demin water, DI water, or DM water — is a type of purified water that has had the minerals usually 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 typically 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.
Deionized water is used in applications where the minerals found 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 crucial.
- Lead-acid car batteries: Because regular 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 using deionized or distilled water 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.
- 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 fewer 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.
- 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 essential for manufacturing makeup and lotions 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.
For home uses, you may be able to substitute distilled water for demineralized water. See our research on where to buy distilled water.