Difference Between Deionized Water And Demineralized Water

Deionized (DI) water and demineralized (DM) water are two types of high-purity water used for various applications. Both process technologies involve the removal of mineral ions from source water to achieve a desired level of purity, but the methods by which they do this differ significantly.

The major difference is that DI water has removed all its ions, while DM water still contains trace minerals. This means that, although filtered, DM water may still contain some dissolved salts and other minerals. DI water has a much lower mineral content than DM water and is considered purer. DI water also has a remarkable ability to dissolve materials due to its lack of ions. Both types of purified water are safe to drink and can be used for various purposes.

What Is Deionized Water?

Deionized water is purified water with its impurities or ions removed. This process removes most dissolved minerals and salts from the source. Removing these ions leaves the water with an almost neutral pH balance. It suits various applications, such as industrial cleaning and cooling, food processing, and healthcare.

What Is Demineralized Water?

Demineralized water, also called distilled or ultra-pure water has removed its ions and minerals through distillation and other filtration processes. This type of water has a neutral pH balance and is considered to be highly pure. Demineralized water is ideal for medical, scientific, and electronic applications where contamination from minerals could be detrimental.

What Is The Difference Between Deionized Water And Demineralized Water?

  • Composition: Deionization eliminates all positive and negative ions from the water, while demineralization removes only certain dissolved minerals. Demineralized water still contains some ions and usually has a higher content of bicarbonates, silicates, and other anionic compounds.
  • Uses: Deionized water is often used in chemical processing applications, such as laboratories and industrial manufacturing because it contains no ions that can contaminate reactions. Demineralized water is used in areas where completely removing dissolved minerals is not necessary or feasible. It is also often used for various medical applications, industrial cooling systems, steam boilers, and reverse osmosis units.
  • Techniques: Deionized (DI) water is created by passing the water through an ion exchange process. This process removes all the cations and anions, leaving only H+ and OH- ions in the water. These two ions are what give DI water its purity. Demineralized (DM) water uses a filtration process to remove impurities from the water. This process typically utilizes filters with a pore size of 0.0001 microns, which is small enough to catch microbial contaminants and suspended particles but also large enough to allow dissolved minerals to remain in the water. As a result, DM water still contains some dissolved solids but at much lower concentrations than untreated water.
  • Costs: Deionized water is typically costlier than demineralized water. However, the long-term savings associated with decreased scaling and buildup make it generally worth the investment.
  • They remove different contaminants: Deionized water removes primarily charged ions, while demineralized water removes both charged and uncharged molecules. Deionization involves passing the water through a bed of ion-exchange resin, which acts like a filter to remove positively and negatively charged particles. Demineralization further reduces the number of contaminants by using an additional process such as reverse osmosis or distillation.
  • The difference in conductivity: Deionized water, also called DI or deionized water, is a type of purified water with its mineral ions removed by passing it through ion exchange resin. It has deficient conductivity levels compared to demineralized (DM) water. On the other hand, demineralized water is a form of purified water that has partially removed its mineral ions. This process results in a higher conductivity compared to deionized water.
  • Different purity levels: Deionized and demineralized water may seem similar on the surface, but they differ in their purity levels. Deionized water has higher purity than demineralized water, as it removes all ions from the water, whereas demineralized water only removes certain ones.
  • pH: Deionized water has a neutral pH, while demineralized water can have a higher or lower pH depending on the process used to remove the minerals.
  • Taste: Deionized and demineralized water are tasteless due to their lack of minerals. However, the two may have subtle differences in taste, depending on the process used to create them.
  • Conductivity: Deionized water has a higher conductivity than demineralized water due to its lack of ions. This means that deionized water can be used for applications where it needs to resist electrical current better than demineralized water.

Uses Of Demineralized Water

  • Laboratory testing: Demineralized water is used in many industrial, medical, and research laboratories for experiments and testing. It can be used to carry out a variety of tests, such as determining pH levels or other chemical components.
  • Cooling systems: Demineralized water can also be used as a coolant in different cooling systems, including computers and other electronic devices. In these systems, the water is usually mixed with a chemical such as propylene glycol to improve heat transfer capabilities.
  • Fertilizers: Demineralized water can also be used as part of fertilizer formulations to provide plants with essential nutrients while eliminating any mineral content that may cause toxicity.
  • Steam irons: Demineralized water is used for steam irons to produce pure, high-temperature steam.
  • Aquariums: It is used in aquariums since it is free of minerals that can potentially produce a nuisance of algae growth. Additionally, deionized water helps to maintain healthier marine life by removing the salts and metals which can be toxic in high concentrations.
  • Fire extinguishers: Demineralized water is used in water-based fire extinguishers because it does not corrode metals, and the lack of minerals helps preserve the water’s overall effectiveness.

Uses Of Deionized Water

  • Ideal for cleaning car parts: Whether you’re an auto mechanic or a DIY enthusiast, deionized water is the perfect choice for cleaning grease and dirt off your car parts. This type of water has been stripped of all impurities, making it highly effective in removing even the toughest grime without leaving residue behind.
  • Used to Reduce Heavy Metal Toxicity in the Body: Deionized water effectively reduces heavy metal toxicity in a person’s body. Heavy metals such as lead, mercury, arsenic, and cadmium can all be toxic when ingested or inhaled.
  • Use it to Wash Your Humidifier: Though deionized and demineralized waters are both low in minerals, deionized water is better suited for humidifier use. Demineralized water can still contain small amounts of minerals that will be deposited in your humidifier over time, reducing its effectiveness. Deionized water is the better choice to avoid mineral residues and keep your humidifier working efficiently.
  • Used in Laboratories for Reagents: Deionized water is widely used in different settings but is most commonly found in laboratories as a reagent. This type of water has had almost all of its dissolved ions removed, which makes it ideal for use in chemical reactions where even trace amounts of these ions could interfere with the results.

Methods Of Water Deionization

  • Co-current Deionization: In co-current deionization, water flows through two beds of ion-exchange resins in opposite directions. The cation exchange resin bed eliminates positive ions, and the anion exchange resin bed eliminates negative ions from water, effectively removing all dissolved minerals.
  • Counter-current Deionization: Counter-current Deionization (CDI) is a process that creates high purity, low mineral content water using ion exchange resin cartridges. This process removes positively and negatively charged ions from the water by exchanging them with hydrogen and hydroxide ions.
  • Mixed-bed Deionization: Mixed-bed deionization is a more advanced form of water purification. The two ion exchange resins are mixed, passing the water through them. As the water passes, all the anions are attracted to one resin and the cations to another, leaving a purified water solution with virtually no dissolved solids.

Methods Of Water Demineralization

  • Distilled Water: Water is heated until it boils, turning it into steam, then cooled to condense the steam into liquid form. The process removes minerals and other solids from the water.
  • Reverse Osmosis: Reverse osmosis is another method used to purify water. It involves passing the water through a membrane that filters out impurities and contaminants from the water.


Is tap water demineralized water?

No, tap water is not demineralized water. Tap water usually contains minerals such as calcium and magnesium, whereas demineralized water has been treated to remove almost all dissolved minerals.

What is the pH of demineralized water?

The pH of demineralized water is typically around 6-7, though this can vary depending on the method used to remove minerals.

Is Aquasana demineralized water?

No, Aquasana water is deionized water.

Does Boiling Water Make it Deionized?

No, boiling water does not remove all minerals and ions, so it will still be considered mineralized or non-deionized.

Where can I buy demineralized water?

Demineralized water can be purchased from many local stores specializing in water filtration systems or online retailers. Researching and ensuring you are purchasing the highest quality product is essential.


Demineralized water and deionized water are processed forms of water that have undergone specific treatments to remove impurities. Generally, the main difference between these two water is that deionization only removes charged particles, while demineralization also targets neutral molecules. Both processes help improve the quality of drinking water, filter out pollutants, and provide a variety of industrial applications. Therefore, it is important to understand which kind of water best serves your needs before deciding.

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