Deionised water vs distilled water: what’s the difference?

Deionised water and distilled water are two of the most popular types of purified water, but what’s the difference?

What is deionised water?

Deionised (DI) water, also often referred to as demineralised (DM) water, is water which has been treated in order to remove ions, leaving behind water with a high purity level. But what is deionised water used for? The filtered water can be used in a number of different ways where highly pure water is required, including in the food and beverage industry, and in cooling systems. 

What is distilled water?

Distilled water is water that has been stripped of impurities. To do this, the water is boiled and the collected steam is then condensed back down into a liquid. Because the impurities within the water have a higher boiling point, they do not vaporise. This means that once the vapour is condensed back down, the impurities and minerals are no longer present. 

Is deionised water the same as distilled water?

No. Deionised water and distilled water are two of the most common types of treated water. Both have very high purity levels and can be used for similar applications, so while many assume they’re the same thing, this isn’t the case.

Deionised water and distilled water are both created in different ways. Deionised water is created in a plant that contains two pressure vessels: one containing cation and the other anion exchange resins. Raw water passes through the cation and positively charged ions and chemically exchanged for hydrogen ions. It continues to the anion vessel where negatively charged ions are chemically exchanged for hydroxide ions. Together, the hydrogen and hydroxide ions create pure water.

For distilled water, water is heated until it turns to vapour. It then condenses back into water, leaving any mineral residue behind and creating a pure supply of water.

What is the difference between deionised water and distilled water? Can I use deionised water instead of distilled water?

We know that deionised water and distilled water are made in different ways, but are they interchangeable? The answer differs depending on the application – yes, there are some instances where either one could be used, but not always. These include:

  • Cleaning and sterilising purposes
  • Automotive applications
  • Medical applications and in the pharmaceutical industry

Deionised water is extremely pure; generally purer than distilled water. This makes it more popular in industrial applications. However, it can be corrosive and have a lower pH. Distilled water isn’t corrosive, so it’s often used in metal-working industries. 


Can you drink deionised water? What about distilled water?

We wouldn’t recommend drinking either deionised water or distilled water. Distilled water is generally safe to drink, however, you’ll probably find it doesn’t taste good due to it having been stripped of important, healthy minerals like calcium and sodium.

There’s some debate about whether deionised water is safe to drink, but we wouldn’t advise it. Like distilled water, it doesn’t contain healthy minerals, so you’ll likely find it doesn’t taste good. It also can be corrosive and can be damaging to the body, due to its lower pH.

We hope this taught you a little more about the differences between deionised water and distilled water. If you have any more questions about deionised water vs distilled water, we’re here to help.  Get in touch today.