Distilled Water Vs Deionized Water

Tap water is purified water that has many minerals, ions, sodium, calcium, magnesium. We use tap water for drinking purposes as the minerals left in the water are good for health. Other minerals which are not safe are removed during purification as per World Health Organization (WHO) guidelines. But this water cannot be used for laboratory purposes. The ions and organic compounds present in the water may interfere in the laboratory analysis and reduce the performance of the application and sometimes lead to inaccurate results.

Water purification system for the laboratory is essential for all the laboratories such as life science laboratory, analytical laboratory, or general chemistry laboratories. Water is used in the laboratory for various purposes such as preparing samples, prepare eluents, preparing the blank, standards, and cleaning equipment or glassware that is used for laboratory analysis. Lab purified water helps laboratory analysis for better performance and accurate results.

Lab water purification systems commonly use different methods such as Reverse Osmosis, activated carbon, ion exchange, distillation, deionization, and more. Here we are going to discuss What is distillation and deionization? How does it work and their differences?

Distillation and deionization is the method used in the water purification system for the laboratory. In both processes, the ionic impurities are removed but the purified water is produced distinctly in different ways to remove ions. Both the distillation and deionization produce lab purified water. Both the process has its own advantages and limitations. It is important to understand when to use each type of water purification system for the laboratory. 

How Distilled Water Works?


Distilled water produced by the laboratory water purifier is the purified form of water that is obtained through the distillation process. Distillation is not a chemical reaction, it involves changes of water from one state to the other i.e., from liquid to vapour and again condensed to liquid form to get purified water.

The distillation process is the process of boiling water that contains salts or impurities above the boiling point of the water and the water is converted into water vapour in this stage. This water vapour is then passed through the cooling chamber and the vapour is condensed again as water is collected. The collected water from the distillation process is free from impurities and salts.

Distillation is considered to be a physical separation process that separates water from other impurities and produces distilled water. The source water used for the distillation process is tap water. The impurities present in the feedwater is to be taken into consideration because some impurities like volatile organic or mercury are vaporized along with the water.


  • Removes contaminants to a large extent
  • Reusable
  • Lower cost


  • Some contaminants that have the same boiling point as water is vaporized with water can be carried into the condensate
  • Careful maintenance is required to ensure purity
  • Requires more heat / electrical energy to boil the water.
  • Requires large space on the counter
  • Slower process

How Deionized Water Works?

Deionized water

The Deionization process used in the laboratory water purifier produces deionized water using tap water or distilled water as a source. The water is passed through an electrically charged ion exchange resin with positive (Anode) and negative (cathode) charged resin where the cations present in the water are attracted towards the cathode and the anions in the water are attracted towards the anode. By this process, the ions present in the water are removed and produce deionized water.

The deionized water produced is highly reactive and get easily contaminated when exposed to air. It reacts easily with gases such as CO2 in the air to produce H+ and HCO3-.

Deionization does not remove molecular particles and microorganisms such as bacteria or viruses and it can be removed with techniques such as reverse osmosis and ultrafilters.


  • Effectively remove dissolved ions in the water.
  • Able to regenerate resin beds
  • Low-cost investment


  • Do not remove particles or bacteria.
  • Operating costs increase when used for the long term.

Distilled Water Vs Deionized water

  • Cost Differences

When considering the cost required for both the distillation and deionization process as the laboratory water purifier, the distillation process takes a long time when a large amount of water is to be purified. This distillation process requires a lot of heat or electrical energy to boil the water. When distilled water comes in contact with atmospheric air, it essentially becomes deionized water. Large space is required to set up the distillation process.

On the other hand, the deionization process is very fast. Usually, in the lab water purification system, two ionized cartridges are used to ensure that all ions are removed. Energy or power requirement is very less compared to the distillation process. Deionization is the chemical process, if the deionization resin is regenerated periodically then the operating cost increases over the long run. Space requirement for the deionization process is very less as it used with the running water and the water needs to be passed through the resin only once to get the deionized water. Storing deionized water is difficult as it is highly reactive when exposed to the air.

  • What Gets Removed?

Both distilled water and deionized water are very pure. In the case of the deionization process, it removes only ions and charged organic particles from the water. The water should be pretreated with Reverse Osmosis (RO) and ultrafiltration to remove organic compounds and microorganisms like bacteria or viruses. With the RO process, all the contaminants present in the water are removed. After this RO process, the water contains only a little amount of ions to remove. When the deionization process combined with the RO process it completely removes all the contaminants from the water to a negligible level.

The distillation process can remove the impurities like ions, chemicals, salts, bacteria, and other minerals present in the water. It does not mean that it removes all the impurities. If the chemicals or volatile organic substances have the same or less than the boiling point of water then these impurities will evaporate and mix with the distilled water. In the case of deionized water, pretreatment filtering is essential in the distillation process as well.

  • Uses

Both processes produce lab purified water. Choosing the best process depends on how the water is used. Distilled water is purer compared to deionized water when the water is pretreated especially in the case of double and triple distillation. And it is pure enough to be used in all laboratory applications But deionized water is not pure enough, it is used in cooling applications, laboratory uses, pharma industries, batteries, and more.


Distillation and deionization is the older process to get purified water. Distilled water purification system laboratory produces pure water by  comparison to the deionized water purification system laboratory as it removes all contaminants like organic, inorganic and microorganisms from the water. Deionized water removes only ionic contaminants from the water and does not remove other contaminants.  

Deionized water is prepared quickly and the cost is less compared to that of distilled water purification system laboratory use. With the combination of other methods like RO, UV photo-oxidation, and more, a deionized water purification system laboratory can produce a higher grade of lab purified water for laboratory use.

Nowadays lab water purification systems with the best combination of different methods produces an ultrapure water system. Techniques such as RO, deionization, activated Carbon, UV photo-oxidation are used in the ultrapure water system to produce ultrapure water that is applicable for all laboratory applications. The oldest method of distillation is replaced by artificial intelligence integrated with lab water purification systems. Lab Q water provides a lab water purification system with different grades of water as such it is used in different applications.

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