Is Reverse Osmosis (RO) Water Demineralized?

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Reverse osmosis is a very thorough water purification process.

But does reverse osmosis also remove minerals from water?

In other words, is reverse osmosis water demineralized? Let’s find out!

Key Takeaways

  • Yes, reverse osmosis water is demineralized. That’s because reverse osmosis removes minerals from water very effectively.

Is Reverse Osmosis (RO) Water Demineralized?

So, is reverse osmosis water demineralized? Yes, reverse osmosis water is demineralized.

Reverse osmosis is such a thorough filtration process that it removes pretty much all impurities and contaminants from water. This also includes minerals such as calcium, magnesium, and bicarbonates.

How does reverse osmosis work exactly? It uses a semipermeable membrane with tiny pores which, under high pressure, only allows water molecules to pass through while rejecting anything else. The rejected impurities/contaminants are flushed away in a wastewater stream.

What Is Demineralized Water?

Demineralized water is simply water that has had its mineral contents removed. Note that this does not refer to any other contaminants – demineralized water can still contain things like bacteria, viruses, heavy metals, pesticides, etc. Still, demineralized water is noticeably purer than regular tap or well water due to the removal of minerals alone.

water on white background

How Is Water Demineralized?

Water can be demineralized in various ways: through distillation, deionization, reverse osmosis, water softening, and oxidizing filters, among others. We’ve focused on the three most effective methods below – those are the ones currently used in most places where demineralization happens.


Distillation is one of the oldest methods for purifying water, and still one of the most effective ones to this day. It’s also very simple – water is allowed or forced to evaporate in a closed vessel with an outlet at the top. Vapor exits the vessel through this outlet and is condensed back into liquid form in another container. Since evaporation at low temperatures almost only affects water and none of the impurities mixed into it, all of these impurities – including minerals – get left in the original container.

Deionization (DI)

Deionization is a more complicated process that involves passing water through ion-exchange resins, which can be one of two types – cation or anion, referring to the charge of the ions attracted (positive or negative).

Minerals present in water sources are either positively or negatively charged ions, which means that they can be removed through deionization. In the process, affected ions are swapped out for OH- and H+ ions, which subsequently form H2O upon combining – or pure water.

Reverse Osmosis (RO)

As mentioned before, reverse osmosis is a popular method for filtering water that relies on a thin, semipermeable membrane. The main feature of this membrane are the tiny pores lining it, which are so small that only water molecules can pass through them. When water is pushed against this membrane at a high pressure, nothing else can make it through the pores and gets left behind as a result.

The only downside to reverse osmosis is that it wastes a lot of water – the process typically converts around 20% – 40% of filtered water to fresh water.

What Minerals and Salts Does Reverse Osmosis Remove from Water?

Reverse osmosis removes minerals and salts very effectively, often to more than 95%. Here’s a list:

Aluminum 97-98%
Aluminum 97-98%
Ammonium 85-95%
Arsenic 94-96%
Bicarbonate 95-96%
Boron 50-70%
Bromide 93-96%
Cadmium 96-98%
Calcium 96-98%
Chloride 94-95%
Chromium 96-98%
Copper 97-99%
Cyanide 90-95%
Fluoride 94-96%
Iron 98-99%
Lead 96-98%
Magnesium 96-98%
Manganese 96-98%
Mercury 96-98%
Nickel 97-99%
Nitrate 93-96%
Phosphate 99+%
Potassium 92%
Selenium 97%
Silica 85-90%
Silicate 95-97%
Silver 95-97%
Sodium 92-98%
Sulfate 99+%
Sulfite 96-98%
Zinc 98-99%

Is Demineralized RO Water Bad for Health?

Many people are concerned about switching to demineralized RO drinking water, believing that their health will be negatively affected. Is that true?

Well, low-mineral drinking water can increase the elimination of sodium, calcium, potassium, magnesium, and other minerals/ions from our body. Thus, the WHO recommends remineralizing low-mineral water before you use it for cooking or drinking (add at least 20-50 mg/l (ppm) of calcium and 10-30 mg/l (ppm) of magnesium).

If you have any thoughts about the question, is RO water demineralized, 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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