Is Reverse Osmosis (RO) Water Demineralized?
Written by: Alexandra Uta // Last Updated: Aug 25, 2023
This page may contain affiliate links. If you buy a product or service through such a link we earn a commission at no extra cost to you. Learn more.
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!
Contents
show
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.
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
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.
Further Reading:
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
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.