What is the Difference between Distilled Water and Deionised Water?

Wave crashing on a rock

It might seem odd to think that the clear, odourless liquid on which we depend as humans can come in so many different forms, yet that is indeed the case.

The tap water we drink, for example, is almost useless in a lab where water is used in experiments, for cleaning purposes or to make other chemicals much purer.

Distilled water and deionised water are both forms of purified water, but to understand the difference between them, we first need to understand exactly what they both are.

What is Distilled Water?

Distilled water, as the name suggests, is water which has had its impurities removed via a process called distillation. In the distillation process, water is boiled and the steam created is condensed into a clean, sterilised container.

This is a process that has been used for more than 2,000 years when our ancestors distilled sea water to create something more potable. The distillation process removes salts, along with most minerals and other impurities, leaving solid contaminants behind. Distilled water is very pure, and can be purified further through double distillation.

Distilled water is used as a cooling agent in car engines, in laboratory experiments, to clean medical tools, make soap, in canned fruit and veg, and in brewing beer, amongst many other things.

What is Deionised Water?

Deionised (or demineralised) water is made by running water through an electrically charged resin which switches hydrogen and hydroxide ions for dissolved minerals, before recombining to produce deionised water. This method is called deionisation.

The process creates a purified water that has had almost all of its mineral ions removed, such as sodium, calcium, iron, and chloride. It does not, however, remove most bacteria or viruses.

Uses of deionised water include as a cooling agent in medical devices, in cleaning industrial machinery, in some aquariums and in cosmetics.

Distilled and deionised water are in many cases interchangeable, although distilled (or double distilled) water should be used if an extremely pure form of water is needed.

Water droplets

What is the Difference between Distilled Water and Deionised Water?

Distilled and deionised water are both forms of purified water. The main difference is that in distilled water, most bacteria and viruses have been removed while some minerals are left behind.

The deionisation process, in contrast, completely removes minerals from the water but doesn’t remove most bacteria or viruses.

Distilled water is normally more expensive than deionised water as the production process takes longer, especially on an industrial scale. Deionisation is much quicker and more efficient, and therefore deionised water is cheaper. It is therefore more commonly used when distilled water isn’t essential.

Can you Drink Distilled or Deionised Water?

Some people do prefer to drink distilled water, but it lacks the minerals found in both tap and spring water and these minerals have both health and taste benefits.

However, deionised water should not be consumed as its “highly aggressive” properties mean it can cause adverse health effects, according to the World Health Organisation.

In addition, deionised water could still contain bacteria and viruses – not things you generally want to put in your body.

Distilled water vs deionised water

ReAgent makes both deionised and distilled water (neither for drinking). We are internationally recognised for our high quality products and first-class customer service, so we’re a company you can count on. 

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