Demineralized Water vs Reverse Osmosis Water

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Even though some people might occasionally refer to reverse osmosis water and demineralized water interchangeably, they are not really the same thing.

Let’s shed some light on the similarities and differences of reverse osmosis vs demineralized water and find out which one you should use!

Key Takeaways

  • Demineralized water is water with low or no mineral content.
  • Methods to demineralize water include distillation, deionization, nanofiltration, and also reverse osmosis.
  • Reverse osmosis water is one type of demineralized water.
  • Reverse osmosis not only removes minerals from water but also potentially harmful contaminants.

Demineralized Water vs Reverse Osmosis Water – Differences

The main difference between demineralized water and reverse osmosis water is that demineralized water is specifically stripped of its mineral contents, while reverse osmosis water is filtered more thoroughly and, theoretically, contains no more impurities/contaminants at all.

Also, there are different methods to demineralize water, one of which is reverse osmosis. But there’s also distillation, deionization, etc. On the other hand, reverse osmosis water can only be produced using reverse osmosis.

The applications of demineralized water and reverse osmosis water also differ. Demineralized water is used where you need water with low mineral content, such as in swimming pools, whereas reverse osmosis water is basically free from minerals and any harmful contamination making it suitable for drinking water production etc.

water on white background

What Is Demineralized (Deionized) Water?

Demineralized water has been treated to remove most to all minerals from it, like calcium, sodium, magnesium, bicarbonate, fluoride, iron, copper, and various others.

In other words, water demineralization is achieved through specific treatment methods that focus on removing minerals. Some of those methods may also remove other impurities, while some are specifically focused on minerals alone.

The amount of minerals left in demineralized can water go below 10 ppm (TDS).

By the way, demineralized water is also called DM water or demin water.

Demineralization is sometimes confused with deionization. However, just like reverse osmosis, deionization is only one way to demineralize water.

How Demineralization Works

Water demineralization can be done in multiple ways, such as:

  • Distillation is probably the simplest example. Water is evaporated from one container into another, and condensed back to liquid in the second container. Since the vapor only contains water molecules and nothing else, the second container ends up filled with pure, clean water.
  • Ion exchange deionization is another commonly used approach, which involves the use of special resins that attract positively and negatively charged ions from water, swapping them out with OH- and H+ ions that then combine into water. Another way of deionization is electro-deionization which is based on electrodes.
  • Reverse osmosis is also an option, and it’s especially popular in cases where more thorough water purification is required and water must be filtered as much as possible. More on that below.
  • Finally, we have nanofiltration which, similar to reverse osmosis, is a membrane filtration method that removes minerals mechanically (via size exclusion).

What Is RO water?

Reverse osmosis water is water that’s been passed through a reverse osmosis membrane. The result is pure, fresh water without any impurities or contaminants – including minerals. Reverse osmosis water is very popular in places with heavily contaminated natural water sources and is thus often used by domestic users for household filtration. But there are also plenty of commercial and industrial applications of reverse osmosis which we’ll discuss soon.

How Reverse Osmosis Works

Reverse osmosis is a bit complicated to implement due to the materials required, but it’s actually a simple process beneath the surface. It all boils down to the reverse osmosis membrane – a special filter element lined with very fine pores that are so small that only water molecules can pass through them. This happens when water is pushed against this membrane at a high level of pressure. All contaminants in the original water stream are rejected and get sent away.

blue reverse osmosis membrane

Applications and Benefits of Demineralized Water

Minerals in drinking water provide a health benefit which is why demineralized water plays a minor role in home environments. However, many commercial and industrial processes require water with low or even no mineral content:

  • Demineralized water is used in producing certain types of batteries. If regular tap water was used, the ions/minerals in the water would react with some of the batteries’ chemicals and shorten their lifespan significantly.
  • Another application of demineralized water is in the pharmaceutical industry – to produce drugs. Without using demineralized water, product safety and overall quality could not be guaranteed.
  • The beverage industry uses dm water to sanitize machinery in order to avoid contamination.
  • Demineralized water is also used in high-pressure boilers, swimming pools, cosmetics production, aquariums, hospitals, and many other places.

Applications and Benefits of RO Water

Reverse osmosis water is pure water with almost no minerals but also no harmful contaminants mixed in. The benefits of that should be obvious for the end user, especially if you live in an area with particularly heavy water contamination.

In addition, many desalination plants around the world use reverse osmosis as their primary tool. On an industrial scale, the process is easy to scale up and quite cost-effective.

Other applications of reverse osmosis include:

  • Pesticide production: Water quality significantly affects the performance of pesticide sprays – think solubility and absorption rate.
  • Brewing industry: The quality of water used for brewing beer is vital.
  • Aquariums: Stable water quality is essential for maintaining aquatic life.
  • Car washes: Without mineral removal, the water in car washes would leave white stains and spotting on the vehicles.

RO Water vs Demineralized Water – Which Is Better?

So, RO water vs demineralized water – which of the two is better? None really.

Reverse osmosis water and demineralized water are just different, and which of the two to use should depend on the application (see above).

If you want to improve the quality of your drinking water at home, reverse osmosis is the way to go.

If you have any questions about RO water vs demineralized water please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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