Deionized water is more common than you think, from your cars radiator and battery, through to beverage production and cleaning your windows!

Water that has been deionized is used in applications that require pure water for it’s low residue levels, for the removal of chemicals that can be harmful to certain processes or for consistency in quality,


Deionized water is water that has had most of the impurities removed through a process of ion exchange. Deionized water is often referred to as demineralised water or DI water. It is considered to be pure water and can be comparable to distilled water.

The process of deionization alone does not remove non-ion contaminants or filter our suspended solids.


When you compare deionized water vs distilled water you would be forgiven for thinking they were the same. Both are types of “purified” water but are produced in very different ways. As discussed, deionized water is produced by passing water over beds of electrostatically charged resins. Distilled water is produced by boiling water until it evaporates, then condensing the water vapour back to water in a 2nd sterile container, leaving any impurities in the original vessel the water was boiled in.

Distillation removes nearly all impurities, where the boiling point is greater than that of water.

When you are comparing the suitability of a distilled or deionized water system consideration needs to be given to the input water quality  (does it contain large amounts of organic matter that deionization alone may not remove?) and the application the water is needed for (will it be for human consumption?)

Distilled water is also considerably more expensive and energy intensive to produce and takes longer vs deionized water.

Water Distillation
Water Distillation

Deionized Water System – Single PS-300

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£269.00 Price incl. VAT: £322.80



Deionized water is made by passing water over beds of ion-exchange resin beads. The beads are either cation (positively charged) or anion (negatively charged). The beds are either separate or have the cation and anion beads mixed (mixed bed). As the water passes over the beds any impurities are attracted to the oppositely charged bead, in a process of ion-exchange, removing them from the water.

Over time the resin beads become “exhausted” as their ability to attract more impurities diminishes, with a decreased quality of the output water.

Industrial systems often have an automated process for the regeneration of the resin. The processes use hydrochloric acid and sodium hydroxide. More commercial systems require the replacement of a deionizer cartridge or the resin itself.

Dependent on the final use it is sometimes necessary to pre or post treat the water in order to remove other impurities, such as microbiological matter. In some applications deionization will be used in combination with either or both reverse osmosis and distillation to produce very pure water or ultra pure water (UPW).

There are also different levels of deionization, it is important to match the correct output quality to the application. If extra pure water is required the deionization process can be repeated multiple times.

Commercial Deionized Water System
Commercial System


The purity of deionized water is measured by its electrical resistance. As it is the ions in the water that determine its ability to conduct electricity, the lower the concentration of ions the lower the conductance (or higher resistance).

The output purity of a given water deionizer system will be dependent on several factors, mainly the technology, actual system used and input purity of water. It is important to check with the manufacturer what the expected purity is and ensure this is suitable for your application.


In principle drinking deionized water doesn’t cause short-term harm. If you were stuck on a desert island and the only water you had was deionized water (OK unlikely we know!), then drinking it is safe.

But dependent on the system used to produce it traces of the resign could be present in the output water, so not advisable to drink it unless it has been specifically produced for human consumption.

There is mixed reviews and research on the long-term health benefits of drinking deionized water. In the pro corner health advocates will say the deionization process will remove harmful contaminants that “could” be present in tap water. In the con corner other health advocates will say tap water contains important minerals that are needed to maintain long-term health.

Deionized water also acts as a solvent, due to it having few ions. It will try to “balance” itself by leaching ions from its surroundings, which, if you have drank it, will be you! It will take minerals from your body as it re-balances its ion levels.

We would recommend doing your own research, and possibly getting medical advice, when deciding what is best for your own personal circumstances. Unless you are on the desert island!


Buying deionized water comes with certain issues, namely remembering to order it, costly shipping, handling of heavy weights, space for storage and shelf life.

The shipping costs are often more than the water itself. After all a 25l container of water is 25kg in weight.

But if you need low volumes, and it wont need to be stored, then it is a cost effective means to buy deionized water.

When you receive the water be sure to check the quality meets your requirements, see above for more details.

If you need higher volumes, or don’t have the storage space for lots of containers, then it is more effective to buy your own deionized water system.

Buy deionized water
Car Battery Water


Having your own deionized water system mitigates the issues of purchasing it by allowing you to produce what you need when you need it.

There are many different deionized water systems available on the market, making it very cost efficient to produce water on demand on your own premises.

Most types of system, such as the HydroPure, have a simple method of changing over cartridges, not requiring any specific technical expertise.

The system will notify you of the output water quality, some systems use LED purity lights or the resin may change colour.

The main criteria will be the output volume and purity of deionized water you need. Will you need it for occasional use or on an industrial scale. For industry or food production?

image of an industrial deionized water system
Industrial System


It is important to ensure that the system you purchase meets your needs in both volume output and purity level. Also on your technical capability to install and run the system.

Be sure to check the technical specification and ask for clarification if anything isn’t clear.

If you require advice on choosing the right system for producing deionized water then feel free to contact us on

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