What is Deionized Water, What Is It Used For, and Is It Safe to Drink?

Find out everything you need to know about deionized water to determine if it’s the best choice for your home.

By: Maggie Pace

In the mid-2010s, nearly 100,000 residents of Flint, Michigan were exposed to lead-contaminated tap water. Their symptoms ranged from hair loss and skin rashes to depression and anxiety. The crisis, which lasted five years, shined a spotlight on the importance of having safe, clean water available in the home.

Water filtration played a role in managing the Flint crisis. As the city worked to clean up the contamination, Flint residents were given water filters certified to remove lead. The filter program sparked questions about water purification — including whether filters work and which filtration processes are suitable for drinking water.

When talking about water filtration processes, deionization comes up often, but is easily misunderstood. For example, a quick online search reveals that deionized water is used in labs and medical applications. That alone could convince you that deionization is the best way to filter water — which isn't entirely accurate.

Here's a closer look at deionization, including how deionized water is used and whether it's safe for drinking.

What is deionized water?

Deionized water, also called deionised water, DI water, or demineralized water — is water that has had ions removed. Ions are molecules with a positive or negative electrical charge. In water, they appear as dissolved mineral salts. Minerals commonly found in tap water include calcium, magnesium, iron, sodium, chloride, sulfates, nitrates, carbonates, and silica.

High concentrations of these minerals create hard water. If you've ever had hard water in your home, you know it's difficult to manage. When hard water dries on surfaces, it can leave a scaly residue that's hard to clean. Hard water is also corrosive, not only to your appliances and fixtures, but also to your skin and hair.

In deionization, water is pushed through a tank or cartridge that's lined with positively and negatively charged resin beads. The beads attract ions with the opposite charge, essentially pulling them from the water. The water runs through the system, and the ions stay behind. This process is called ion exchange.

Notably, deionization only removes ions. Uncharged contaminants and suspended solids, including viruses and bacteria, can remain in deionized water.

Is deionized water the same as distilled water?

Deionized water is not the same as distilled water. Both deionized and distilled water are purified, but through different processes — distillation uses heat while deionization uses ion exchange.

Distillation heats the water until it vaporizes. The vapor separates from dissolved minerals, suspended solids, and other impurities. Those remain in the original container, while the water vapor is captured elsewhere. The pure vapor is then cooled back to liquid water. Distillation removes minerals as well as viruses, bacteria, and other organisms.

Deionized water uses ion exchange to separate water from molecules with a positive or negative electrical charge, typically minerals. Since only ions are removed, uncharged contaminants including solids, viruses, and bacteria will remain in water.

What is deionized water used for?

Deionized water is ideal for applications that require precise chemistry, since removing all ions (except H2O) makes it chemically pure. Water that's free of impurities will produce more reliable, repeatable results in lab experiments and manufacturing applications. As a result, medications, cosmetics, and even production beverages may use deionized water.

There are also good ways to use deionized water in your home:

  • Filling a dehumidifier to avoid mineral buildup.
  • Cleaning countertops, windows, and other surfaces without leaving a residue behind.
  • Filling your aquarium.
  • Making DIY shampoos, face washes, and conditioners.
  • Cleaning car parts.

Is deionized water safe to drink?

Deionized water is safe to drink, but it's not your best option for three reasons:

  1. Lack of minerals: Deionized water lacks minerals that are good for you, such as calcium, magnesium, and iron. You can easily take in these minerals from a well-rounded diet, but it doesn't hurt to have them in your water, too.
  2. Flat taste: Removing minerals also affects the taste of the water, and deionized water doesn’t taste great. The taste difference is hard to describe, but some say deionized water tastes "flat" or "off."
  3. Remaining contaminants: Deionized water may still have organic compounds — including viruses or bacteria — that can make you sick. This sounds counterintuitive, given that deionized water is thought of as "pure." But "purity" with respect to deionization means the water is free from charged molecules. As noted, the deionization process does not remove uncharged organic compounds.

A better choice for in-home water

Deionized water has its uses, but for the reasons noted above, it’s not recommended for in-home use. The right filter is one that removes the dangerous contaminants, leaves healthful minerals, and produces water that tastes great.

The OptimH2O® from Aquasana, a whole home filter, has those capabilities. It removes 99% of lead and cysts, 98% of PFOA and PFOS, and 90% of chloramines.

  • Cysts are microorganisms found in water. Giardia and cryptosporidium are two common ones, and both can cause digestive irritation.  
  • PFOA is perfluorooctanoic acid. PFOS is Perfluorooctane Sulfonate. Both are chemicals commonly found in drinking water. They are associated with cancer, immunity deficiencies, and thyroid imbalances.
  • Chloramines are disinfectants used by water utilities to treat drinking water. The EPA has studied the health effects of chloramine and has established maximum contaminant levels for drinking water.


Tested and certified to reduce lead, cysts, and PFOA/PFOS, plus tackles chlorine and chloramines.

Water filtered through the OptimH2O is much cleaner than tap water but doesn't have the flat taste of deionized or distilled water. It's gentler on skin and hair and easier to cook with, too.

Deionization purifies water, but it's not the type of purity you need for drinking water. An effective water filter, on the other hand, delivers the benefits of deionization without the drawbacks.