reverse osmosis

Reverse Osmosis (RO) water filters

Thinking about buying a RO (Reverse Osmosis) water filter? Want to know how RO works? Is there a better alternative? Is it healthy to drink water from a RO filter?

We clarify the basics that you need to know.

What is RO?

The technology was originally invented as a solution to

  1. Desalinate brackish water or sea water to make it drinkable
  2. Reduce very specific chemical contaminants such as heavy metals

RO is a process through which water pressure pushes the tap water through a semipermeable membrane that allows relatively small water molecules, but not larger molecules such as dissolved minerals (e.g. Salt) to pass through.

What does Reverse Osmosis filters remove?

RO systems remove pollutants from water including nitrates, sulfates, fluoride, arsenic and much more. But it also removes healthy minerals such as magnesium, calcium, potassium and sodium.

Generally claims around what RO removes is based on high pressure industrial RO filters so therefore lower cost housefilters may not be as effective.  

It does not remove chlorine or soften the water and therefore activated carbon filters are almost always required in combination of RO. The activated carbon also helps remove 70+ other contaminants such as pesticides, herbicides, chlorine bi-products, pharmaceuticals and more.

RO filters reduce TDS

“The sales guy used a TDS tester to justify the need for a RO system”

TDS measures the amount of dissolved substances in the water. Often the sales technicians use this as an argument for needing a water filter. The problem is that TDS is not a good measurement of clean water. A TDS of 150 ppm for example normally just means that the tap water is high in minerals which is good.

Read more about TDS as a water quality measure.

Do I need a RO filter to get clean drinking water at home?

Over the past 10-15 years RO systems combined with activated carbon have been marketed as the only solution for household drinking water. In reality RO filters are often a waste of money and water for most households.

Before purchasing an RO unit or any other water treatment equipment check the quality of your local tap water and what is required to make it safe and tasty.

What are the disadvantages of RO?

  • Wastes as much as 6x the amount of clean water produced
  • Requires professional maintenance to ensure effectiveness and safety
  • Filters usually need to be replaced once every 3-6 months
  • Removes healthy minerals
  • Relatively expensive starting from $300 + maintenance and replacements
  • Risk of bacteria growing in the water after the filter since the chlorine has been removed

Here’s what a typical RO installation looks like along with some of the maintenance requirements. Fast forward to 13:35 to see if RO operation and troubleshooting.

Is demineralized water produced by reverse osmosis good for you?

No, it’s actually not. According to the World Health Organization, low (TDS) water produced by reverse osmosis or distillation is not suitable for long term human consumption and in fact, can create negative health effects to those consuming it. This lack of minerals may also impact the taste negatively for many people.

Read more about minerals in tap water.

What are the alternatives?

Most of the tap water in e.g. Europe and North America is already potable (drinkable according to strict WHO, EPA and EU standards). Therefore the first priority is usually improving taste and reducing risk of possible contaminants such as THMs, microplastics and heavy metals.

A high quality activated carbon filter will take care of this with the following advantages

  1. can easily be installed and replaced by anyone
  2. cost considerably less
  3. doesn’t remove the healthy minerals from the water
  4. don’t waste any water
  5. lower risk of water going stale

Examples activated carbon filters include TAPP.

TAPP 2 is an alternative to reverse osmosis filters

There are also other alternatives such as Ion Exchange, UV purifier, Ozone and distillation. Read more in this water filter guide.


Reverse Osmosis is an amazing technology innovation providing fresh water from sea water in areas around the world where water is a scarcity and for industrial cleaning of contaminated waste water. It can also be a good solution for clean household water when the conditions require.

However, in most cases the municipal water is safe to drink and a quality activated carbon faucet filter will provide fresh and tasty tap water at a lower cost and with less waste.

Contact us if you have comments/questions.


WHO report on Demineralised water 

Water waste and other disadvantages of Reverse Osmosis

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1 thought on “Reverse Osmosis (RO) water filters”

  1. This is a very controversial topic in the water world. The primary argument behind theory seems to be based on one study released by the World Health Organization (WHO). WHO produces international norms on water quality and human health in the form of guidelines that are used as the basis for regulation and standard setting world-wide. There are few health issues of RO water consumption…

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