What is Deionized Water?

Michael Anissimov
Michael Anissimov

Deionized water is a type of purified water with mineral ions (salts) removed. These mineral ions include sodium, calcium, iron, copper, chloride, and bromide. Deionized water is created by taking conventional water and exposing it to electrically charged resins that attract and bind to the salts, removing them from the water. Because most of the impurities in water are mineral salts, deionized water is mostly pure, but it does still contain numerous bacteria and viruses, which have no charge and therefore are not attracted to the electrified resins.

A bottle deionized water, which is made by purifying water and removing the mineral ions.
A bottle deionized water, which is made by purifying water and removing the mineral ions.

In recent years, many deionization systems have been marketed for home use, often with claims that deionized water is an antioxidant that can slow aging and prevent disease. This is quack medicine, and contradicts basic aspects of physiology and chemistry. Some scientists who have studied the health effects of this water have even called it "snake oil on tap." There are many reasons why this water should not be expected to have positive health effects, but one is that the mineral salts that one would avoid by drinking this water are merely regained by eating any other food with even trace amounts of moisture. So the level of mineral salts in the body is essentially the same either way. Many of the mineral salts are essential nutrients, and some scientists even say that drinking unpurified water provides us with significant portions of our daily values of these nutrients.

Steam irons should be filled with deionized water.
Steam irons should be filled with deionized water.

Despite its uselessness for improving health, deionized water has many applications, most of them scientific or industrial. Deionized water is used extensively in microbiology experiments as a medium. This water is also cooked in an autoclave prior to use, which kills off all bacteria or viruses therein. It is used to top up lead acid batteries used in cars and trucks, as mineral ions found in tap water drastically reduce their lifespan. It is used for steam irons used on clothing, ensuring well-ironed clothes without any chance of mineral residue. Deionized water is also used as a medium or additive in many pharmaceutical or cosmetic products, desired for its low chemical reactivity.

Scientists have found no proof to support claims that deionized water has positive health effects.
Scientists have found no proof to support claims that deionized water has positive health effects.
Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Discussion Comments


The deionized water is the form of distilled water that is free from all types of mineral salts from water. These mineral ions include sodium, calcium, iron, copper, chloride, and bromide

A water purifier, on the other hand, has a membrane that removes the excess of the minerals added in the water.

The best option to remove TDS from water is to use hard water softener. A hard water filter, also called a water softener, is designed to filter water to remove excess minerals such as magnesium and calcium that are present in the hard water.

The activated carbon hard water filter creates generally odor-free, pleasant drinking water.


Deionized is the same thing as distilled, but it is created through a different process.


I remember talking to someone once at a cafe who was a friend of a friend and had just been to the local co-op to get some deionized water. They sold it on tap there, allowing people to fill their own bottles for a few dollars.

I don't think this woman really understood what had been done to the water. She thought it had been 'charged' with energy which transferred to her when she drank it.

I guess the placebo effect is really something.


@anon114328 - You can use deionized water filters to make rainwater into deionized water, but rainwater itself isn't naturally free of minerals. It picks things up in the air on the way down and I believe some of the minerals might even last through the whole evaporation process.

That's why evaporation isn't an ideal way to deionize water. Acid rain is a good example of rain water that is obviously impure.

If you do decide you want to drink rainwater, remember that even putting it through this kind of filtration isn't going to be enough to purify it. You need to make sure it isn't going to have viruses, bacteria and other nasties growing in it, which means some other method of purification.


Wow, I can remember seeing one of my uncles with deionized water when I was a kid (he had some kind of deionized water system set up at his house and I was curious about it). I always wondered why he was doing it, and never got around to asking him and now I have my answer.

It must have been something to do with car batteries. He was always messing around with his car.


Reply to raha's question: "why is deionized water a good item for cooling systems?"

If you would use regular water, cooling systems would corrode and clog over time due to the salts and other minerals in the water.


I need information how to prepare the deionized for a industrial purpose of deionized water. Then I have a plan to start a small unit of distilled water. Could you please give an idea.


which has more reactivity: deionized water or drinking water, and why?


Deionized water should, in theory, have no conductivity. If the resins, cations and anions are somewhat depleted, then some ions will pass through. Only particles that hold either a positive or negative charge will be attracted to the resins in the DI tank and thereby be "stuck" and pulled out of the passing water. Some molecules that do not hold a charge will not be trapped in the resin and will pass through.

DI water isn't necessarily good to drink because the closer that you get to pure water, the more reactive the water is with other molecules. It becomes corrosive to things in its environment and can leach minerals from your insides when consumed. DI isn't the best type of water to drink.

DI water doesn't remove, for example, heavy metals and microorganisms. Bacterias and viruses actually are known to foul a DI resin system by driving the PH to extremes and destroying the resins ability to attracted ions. A good idea if you're using a DI system is to attach a carbon filter ahead of the resin tank to destroy microbes ahead of time.


Hey ashish, deionized water and de-mineralized water are the same, they use the same process and produce the same results.


why is deionized water a good item for cooling systems?


Trader Joe's carries deionized water in the bottled water section- though I don't recommend drinking it as your main source of hydration.


"real water" is a deionized bottled water and the health benefits I've experienced are incredible.


can i use rain water as deionized water?


Could the element of deionized water in a lotion

cause a bleaching or spotting of the skin ?


Is the process of deionization a chemical or electrical process?


I want to buy a bottle of deionized water to mix with a hair product. It called for deionized water. Where can I find it. I have been to Target, Randalls...? Thanks. P. Anderson


i have deionized water with the following specification ph(5.5-9)&conductivity <5.5 ms\cm

is it true to use deionized water with zero conductivity?


What is the difference between deionized water and de-mineralized water in terms of pH value and ultrasonic cleaning?

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