What is Deionised Water Used For?

by Dan Wiggins

This time around, we cover what deionised water is used for and what it actually is.

What is Deionised Water?

Deionised water is water that has quite literally had its ions removed. Ions are atoms and molecules that have a net electric charge as a result of losing or gaining more electrons. In easy terms, deionised water has been filtered and removed of its ions, which makes it extremely pure. But what exactly is it used for? Here, we take a look.

Deionised Water Container
Deionised water container

Common Usages

Motor Vehicles

It is commonly used within lead-acid batteries and coolant systems within an engine. With the water rid of ions, it ups the longevity of the battery and coolant system. Normal water would only hinder its lifespan.

Lab Tests

Ordinary tap water is not used within labs due to it not being pure. Instead, the use of deionised water is widespread as it is completely pure and free from ions. It is also used to clean equipment, as to not taint it.

Cooling Equipment

Deionised water is used in cooling systems as it contains no ions. Its lack of ions make it perfect to lower the risk of overheating in certain systems. This is because of how bad a conductor it is.

Putting Out Fires

It is one of the elements inside of fire extinguishers. It is used because of how badly it conducts electricity, making it safe to use around electrical equipment if it is on fire. It is also less likely to damage electrical equipment, unlike regular water.

Fish Tanks

Tap water should not be used in a tank as it isn’t pure like its freshwater counterpart. Deionised water is clean enough to minimise algae, leading to a healthy life for marine critters.

What is deionised water used for - aquariums
Deionised water is of particular use within aquariums.

Cosmetic Products

It is used in creating beauty products in order to lengthen their shelf life. Again, normal water contains too many traces of other things to be used viably within cosmetics.


Cleaning industrial machines is essential. However, regular tap water contains substances which may corrode the machines after time. Using deionised water eliminates this worry completely.


Deionised water is heavily involved in any sort of pressure or steam cleaners. For the pressure side, its lack of ions means it finds it easy to replace them with something else, making it an effective cleaner there. For steam, it lessens the scale of furring and gunk build up within the steamer.


High concentrate mixtures, such as very strong antifreeze, use deionised water in order to dilute it effectively.


As you can see, there are many important uses for deionised water. Although it shares similar properties with distilled water, it is not the same thing. You can find a distinct selection of deionised water by clicking the link below.

For comprehensive information about deionised water, check out our Complete Guide to Deionised Water resource.


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