A Complete Guide to Demineralised Water

What Is Demineralised Water?


Demineralised water is also known as demi or demin water. It is exactly as its name suggests – demineralised water is water that has had its minerals removed.

Which Minerals Are Removed From Water To Make Demineralised Water?

Water goes through a chemical treatment process called demineralisation that removes contaminants, salt and minerals including:

Calcium (Ca2+)
Chloride (Cl–)
Iron (Fe3+)
Magnesium (Mg2+)
Manganese (Mn2+)
Nitrates (NO3–)
Potassium (K+)
Sodium (Na+)
Sulphates (SO42-)


After this process, the demineralised water may still contain organic contaminants such as viruses or bacteria. A higher purity water can be obtained through further treatment of demineralised water.

How Is Demineralised Water Made?

A Complete Guide to Demineralised Water - how is demineralised water made


 

There are a couple of ways in which to make demineralised water:

Making Demineralised Water Through Deionisation

It’s commonly thought that demineralised water is the same as deionised water, but they are two different (albeit similar) products. They can both be made by deionisation, but the main difference is that demineralised water has no minerals and deionised water has no ions.

Deionisation happens when water is passed through a mixed ion exchange bed. In this ion exchange bed, positively and negatively charged resins remove their respective ions. These resins are cation and anion.

Cations are positively charged and remove positively charged ions such as calcium and magnesium from water. Anions have a negative charge and remove negatively charged ions like sulphates and nitrates.

Ions conduct electricity, so it’s important to maintain electrical neutrality throughout the deionisation process. This means that each ion that is attracted into the resin bed must be replaced by an ion that is leaving the resin bead. This is what is called ion exchange.

Making Demineralised Water Through Membrane Filtration

In the membrane filtration process, a semi-permeable membrane captures and removes total dissolved solids (TDSs), including molecules and ions, viruses and bacteria from water. The membrane’s pores allow certain micro-particles to pass through while preventing others from doing so.

Two types of membrane filtrations are used in the demineralisation process to remove these extremely small impurities: nanofiltration and hyperfiltration (reverse osmosis).

Uses of Demineralised Water


A Complete Guide to Demineralised Water - uses of demineralised water in industry

 

The lack of minerals in demineralised water means it has a wide range of industrial and scientific uses because it is unlikely to corrode or contaminate other materials.

Laboratory Applications of Demineralised Water

In the lab, demineralised water is used as a solvent, to prepare buffer solutions, dilute chemical concentrations and act as a cleaning agent for equipment. It’s important to use pure water rather than ‘regular’ water in the lab because it:

  • Ensures that data obtained during testing is precise
  • Maintains the integrity of analyses and products
  • Won’t leave residue on sensitive equipment

This means that demineralised water can help ensure chemical processes are precise, conditions are sterile and results are reliable.

Uses of Demineralised Water in the Automotive Industry

The calcium content in water causes a level of build-up that will eventually corrode metal, so a purer form of water is used in the automotive industry. As demineralised water doesn’t contain calcium, it is used in:

  • Cooling systems of cars and aircrafts
  • Lead-acid batteries
  • Gas-turbine engines

However, it is important to consider whether or not to use demineralised water if you’re using steel products. That’s because demineralised water will corrode steel if it has been contaminated with dissolved gases like oxygen or carbon dioxide. You must always ensure that demin water is protected from atmospheric contact.

Pharmaceutical Manufacturing

When used in pharmaceutical and cosmetic products, demineralised water is called ‘aqua’. Its purpose is as a primary ingredient, to control the quality and safety of other ingredients, and for cleaning and energy transfer purposes.

Other Uses of Demineralised Water

Demineralised water has countless other applications, including:

  • Electronics – to wash circuit boards without contaminating them
  • Petrochemicals – to treat cooling tower blowdown
  • Power industries and refineries – in high-pressure boiler feeds
  • Steam applications such as steam irons
  • Commercial window cleaning as it leaves no residue
  • Laser cutting and laser cooling

Benefits of Demineralised Water


The benefits of demineralised water are closely tied to its uses. Benefits include:

  • High purity
  • Typically non-corrosive (with the exception of steel)
  • Leaves no residue
  • Does not build up-scale
  • Good diluter
  • Quick to manufacture
  • Non-hazardous (in manufacture and in form)
  • Can help reduce production costs

Can You Drink Demineralised Water?


A Complete Guide to Demineralised Water - can you drink demin water

 

Some people do drink demineralised water, believing it to be healthy because of its high purity. However, we at ReAgent agree with the World Health Organisation (WHO). They do not recommend drinking demineralised water – especially demineralised water made to an industrial grade. Industrial grade demineralised water is most certainly unfit for human consumption.

The WHO gives the following reasons against drinking demineralised water:

  • You won’t get the minerals found in regular water, like calcium and magnesium, that your body needs
  • Demineralised water doesn’t quench thirst as well as ordinary water – and it doesn’t taste very nice
  • It has been shown to affect your metabolism, causing tiredness, weakness and headaches; or more severely, muscular cramps and impaired heart rate. Severe acute damage can also occur if you drink demineralised water over a long period of time
  • When demineralised water comes into contact with other materials, it wants to absorb their ions. If demineralised water has come into contact with other chemicals or metals, they may be in the water you drink – this may lead to a risk of metal toxicity. This is especially true if you drink demineralised water from a tap.
  • There is a lower protective (antitoxic) capacity in water which is low in or contains no calcium and magnesium
  • In the same way, if you drink demineralised water it may absorb ions such as calcium and magnesium from the tissues in your body

Our conclusion: this doesn’t sound good. Demineralised water has better uses in industry, science and the laboratory than it does for humans. Please don’t drink it.

Hazards Of Demineralised Water


Demineralised water doesn’t present any hazards in normal industrial use, including physical, health or environmental hazards. It is not flammable, it’s stable, and no classified risks have been identified.

We just recommend that you don’t drink it!

Demineralised Water Specification


DescriptionLimitsUnits
H₂OM.W. 18.01
Conductivity<1.5µS/cm
Chloride<1ppm
Resistivity1/conductivityMohms
pH @ 20°C5 – 8
Conductivity can increase on storage as CO2 can be absorbed.

Demineralised Water Material Safety Data Sheet (MSDS)


Demineralised water is not classified and so doesn’t require a material safety data sheet. At ReAgent, we provide a demineralised water safety data sheet as advice for product users. Under REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals manufactured in or imported into the E.U.), material safety data sheets (MSDS) are referred to as safety data sheets (SDS).

Where To Buy Demineralised Water


A Complete Guide to Demineralised Water - where to buy demineralised water

 

You can buy demineralised water from a variety of places…like ReAgent! Of course we would say that, but in truth there are certain types of customers we wouldn’t be the best supplier for.

Businesses Who Want to Buy Demineralised Water

If you are a business looking for a recognised, reputable chemical manufacturing company to buy demineralised water from, a manufacturer such as ReAgent is most suitable. Why?

  • A chemical manufacturer is an expert and probably supplies a range of high purity waters
  • Reliability is key – ordering several IBCs of demineralised water only for it to be late or off-spec is not something you want to happen
  • You will get advice on the best type of water for your needs – demineralised water may be less suitable than a different high-quality water
  • Making to order means a higher quality product than off-the-shelf sources
  • With ReAgent, you’ll get free pre-purchase technical support and after-sales support
  • Chemical companies often have quality accreditations – at ReAgent we hold ISO 9001 and ISO 14000
  • Reliable couriers mean your order will be delivered on time and in full
  • Certificates of conformity and analysis can be supplied if needed
  • You can create an account and place regular orders easily

However, many chemical companies don’t supply demineralised water direct to consumers which is the case here at ReAgent. We only supply chemicals to businesses.

Consumers Who Want to Buy Demineralised Water

You can buy demineralised water cheaply and easily from many large supermarkets. However, as this type of demineralised water isn’t made to order, the quality is likely not to be as good and it’s only really suitable for when you need to buy a very small amount.

You can also buy demineralised water from online retailers such as Amazon. If you do this, we strongly recommend checking the sellers in detail as you’ll probably find that they aren’t as reputable as established chemical companies. For example, it’s likely that they won’t have the same high quality standards or accreditations.

Buying demineralised water online also means there’s another party in your supply chain, and that can get complicated. It could be difficult to get a VAT receipt, and you possibly won’t get the same (or any) after-sales support.

Disclaimer

The content on chemicals.co.uk and everything published on it is provided as an information resource only. The content, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).

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