Deionized water and distilled water are both types of purified water, but deionized water has had its mineral ions removed through ion exchange, while distilled water is produced by boiling water and collecting the condensed steam.
Deionized water is typically used in industrial and laboratory settings, while distilled water is used in household appliances and medical applications.
Distilled and deionized water are two popular types of bottled water for home and commercial use.
You may have purchased them for a CPAP machine or an aquarium. But while both are of high purity with very few contaminants, they’re not created equal.
What’s the difference, and which is right for you?
Let’s compare and contrast deionized and distilled water.
Key Takeaways:
- Distilled Water: Obtained through a process of heating water to its boiling point and then collecting the steam.
- Deionized Water: Produced by passing water through an ion-exchange resin which removes most ions (minerals and salts).
- Distilled Water: Has no mineral content and is considered “pure” H2O.
- Deionized Water: Has virtually no ionic content, but may contain some dissolved organic matter.
What is Deionized Water?
Deionized, or DI water, has been treated to remove ions — electrically charged particles — from tap water. The net effect is a near-total reduction in the number of minerals. The most common deionization method is similar to the ion exchange process used in water softeners.
Demineralized water is used primarily by industries in which the electrical charge of ions can interfere with the manufacturing process. You’ll find it in laboratories, hospitals, food processing plants and electronics factories where it’s used to lower temperatures in heat-sensitive equipment during production. Its low conductivity also makes it ideal for immersion cooling applications.
At home, deionized water is recommended for aquariums, some types of beer making and to keep steam irons from clogging.
What is Distilled Water?
Distilled water is produced by condensing steam into clean water. Among the world’s oldest and most effective water purification methods, the distillation process removes more than just minerals. It eliminates all substances with a lower boiling point than water, from heavy metals and chemicals to bacteria and many, but not all, volatile organic compounds.
Because of its purity, distilled water is popular for laboratory applications. Free of disease-causing microorganisms, distilled water is often recommended over deionized water for medical devices, such as CPAP machines. A so-called soft solvent, it contains no abrasive mineral ions, so it’s great for cleaning glassware.
Are Distilled and Deionized Water the Same as Purified Water?
According to the Environmental Protection Agency, purified water has a very strict definition. It must be free of all chemicals and pathogens and contain no more than 10 parts per million of dissolved solids, mostly minerals. Therefore, while both distilled and deionized water have fewer impurities than tap water, only distilled water can be called “pure” water.
Distilled vs Deionized Water — Are They Safe to Drink?
Yes, you can drink deionized water and distilled, but both have minor drawbacks to consider.
Contaminants
Distilled water is deionized but not all deionized water is distilled. By definition, deionized water is not required to be pathogen-free, but it’s usually made from a filtered or disinfected source water, so it’s usually no riskier than drinking from the tap when it comes to bacteria. Distilled water, however, may be the better choice, and it’s also lead-free.
Taste
All drinking water contains impurities, and like it or not, we’re used to the flavor. Both the distillation and deionization process remove most minerals, and without them, water tastes flat— like it was boiled.
Deionization also doesn’t remove some molecular species, such as sugar, so not all deionized water tastes the same. Depending on the water source, the difference in the end product can be unpredictable.
Using high-purity water for cooking can make a difference with certain recipes. Distilled water, for example, is often recommended for making coffee. But minerals balance the taste of drinking water, so neither distilled nor deionized water is particularly refreshing to drink.
Nutrition
Minerals in water can wreak havoc on your home, but their health benefits are hard to ignore. Calcium, magnesium and iron are must-haves for the body, contributing to our neurological and cardiovascular health.
The scientific consensus is that we get most of the minerals we need from our food, but given the average American diet, we can use all the help we can get. Neither distilled water nor deionized water has any nutritional benefit.
Potential Health Effects
Distilled and deionized water both have a relatively neutral pH of around 7.0 until they’re exposed to carbon dioxide. As soon as they’re poured, the pH starts to drop and can hit a low of 5.5.
In tests, deionized water has been shown to corrode carbon steel, so imagine what it can do to your teeth and the soft tissues in your mouth. Repeated or long-term contact with tooth enamel has the same effect as drinking acidic beverages.
This issue applies mostly to drinking bottled deionized water because the jugs are repeatedly opened and exposed to air. If you’re drinking soft water from a tap, exposure to carbon dioxide is minimal.
Research from the World Health Organization also suggests that drinking large quantities of deionized water can cause people to urinate more and become dehydrated as electrolytes are eliminated from the body. This, however, applies primarily to people who have no other access to potable water or other bottled drinks, such as after a natural disaster.
Can I Make Deionized and Distilled Water at Home?
Whether you need it for your home business or medical devices, there are advantages to making your own distilled or deionized water. Let’s take a closer look at each process.
Distillation
Distilled water is made by boiling water in the lower chamber of a dual-chamber pot. As the steam rises, it’s captured by a cooling coil and re-condensed as pure water into a separate container. Once the water has boiled away, the contaminants remaining in the lower pot can be washed away. Double and triple distilled water is the most purified water money can buy, containing no dissolved solids, bacteria, chemicals or dangerous metals, like lead.
Home water distillation units are inexpensive and easy to operate. You can purchase one for as little as $79 to make enough distilled water for a CPAP machine or oxygen concentrator. But the distillation process is slow, and it can only produce a few gallons of purified water per day at most — not enough to meet the drinking and cooking needs of most families.
Distillers also require electricity to operate, adding to the production cost. For small-scale use, however, it’s among the most budget-friendly solutions for purifying small amounts of water at just pennies per day.
Deionization
Most deionized water is made at the industrial level by passing tap or spring water over electrically charged resin that removes ions. But unlike conventional water softeners that remove only positively charged ions, there are two resins in a deionizer’s resin bed.
Unique, this mixed bed resin contains both anion and cation resin to eliminate both positive and negative ions by replacing them with hydrogen and hydroxyl molecules. With the ions removed, you have deionized water.
You can purchase an ion exchange deionization filter from a water treatment company, but they’re not cheap. For residential use, a reverse osmosis filter may be a better solution. It gives you demineralized water with the benefit of additional filtration for hundreds to thousands of dollars less.
Reverse osmosis is the same source water treatment method water systems across the country use. Laboratory tests show it’s as effective as water distillation, removing most bacteria and volatile organics.
If you have bacteria, chemicals or other impurities in your source water as well as unwanted ions, an RO filter is among the best solutions for improving your overall water quality.
Deionized Water vs Distilled — The Bottom Line
If you’re worried about contaminants, should you replace your tap water with either deionized or distilled water? That’s a good question.
Either is better than consuming water with bacterial contamination. If you get a boil order from your municipality, you can use it for drinking, cooking and making baby formula. If you have a water softener or a reverse osmosis filter, you’re effectively drinking it now — it’s safe.
If a water test shows lead, using distilled water is an option until you find a long-term solution. But if taste impurities, like chlorine, are your only concern, carbon-filtered or spring water has a better flavor, it’s less expensive, and it’s easier to produce at home.
If you want demineralized drinking water, an RO filter is your best bet. If you prefer the purity of RO water, but want the taste and nutrition of minerals, select a model with a remineralizing cartridge. It adds the minerals the RO membrane removes.
Final Thoughts
The use of deionized water vs distilled may seem like an argument for chemists, but it’s crucial to know that they’re not always interchangeable. The difference is subtle, but it can impact your health, home and medical devices.
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