What Is Demineralised Water?

by Jessica Clifton

If you’re confused by what demineralised water is versus deionised, distilled, ultrapure, purified water (the list goes on)… you’re in the right place.

There are many forms of purified, high grade water, and in today’s blog post we’re going to look in a little more depth at what demineralised water is.

What Is Demineralised Water?

Demineralised water is also called demi or demin water. Essentially, it is exactly as its name suggests – demineralised water is water that has had its minerals removed. As you would expect, it’s a little more complicated than that though…

What Is Demineralised Water

Which Minerals Are Removed From Water To Make Demineralised Water?

Water goes through a treatment process 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-)

The amount of dissolved solids in demineralised water is always less than 10 mg/l. Conductivity is typically less than 2 mS/m and can even be lower.

Once water has been through the demineralisation process, it may still contain organic contaminants like viruses or bacteria. A higher purity water can be obtained through further treatment of demineralised water.

How Is Demineralised Water Made?

Demineralised water can be made in several ways. It is commonly used interchangeably with deionised water. While the two products are very similar because they can both be made by deionisation, the main difference is that demineralised water has had its minerals removed and deionised water has had its ions removed.

As well as deionisation, some of the ways in which demineralised water can be made are:

  • Distillation
  • Membrane filtration (reverse osmosis or nanofiltration)
  • Electro-dialysis

The demineralisation process makes water soft rather than hard, but demineralised water is aggressive on metal, which means it’s normally transported in plastic containers.

Uses Of Demineralised Water

Demineralised water is of sufficiently high quality that it is used in many industrial processes. Lower purity grade water could act as a contaminant in these processes. Additionally, demineralised water is also used when water with a low salt content or poor conductivity is required.

What Is Demineralised Water - use in industrial processes

Examples of demineralised water uses include:

  • Boiler feed water in power plants, refineries and petrochemical companies
  • Laboratory testing
  • Analytical chemistry
  • Cleaning lab equipment
  • Sanitising containers and equipment in the food industry, as well as being used for some food processing


Can You Drink Demineralised Water?

We do not recommend that you drink demineralised water, for several reasons:

  1. As we’ve already seen, demineralised water is aggressive – for example, it would leach metal (and other material) from pipes and storage tanks
  2. Because it lacks minerals, it doesn’t taste nice and doesn’t quench thirst
  3. Demineralised water can have adverse health effects

At ReAgent, we sell demineralised water in sizes ranging from ampoules to 25,000L tankers – none of it suitable for drinking! If you’d like to find out more or to discuss your demineralised water requirements, contact our team today.


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