What is Not Removed by Reverse Osmosis

Reverse osmosis is a very popular water purification method. But, as with any kind of purification process, it cannot remove everything. There are some things that can still pass through a reverse osmosis system.

The majority of the most common contaminants can be removed through reverse osmosis. The kinds of contaminants that reverse osmosis can remove are pesticides. Reverse osmosis can also remove a lot of minerals.

But, there is a good chance that these minerals will still filter through. This will depend on the size of the mineral particles. These particles can be small enough to still pass through the filtration system.

This can also include some pesticides and herbicides. Reverse osmosis is a much simpler process than it might appear. So it definitely isn’t foolproof.

What is Reverse Osmosis?

Before we get into exactly what reverse osmosis can and cannot remove, let’s go over exactly what reverse osmosis is.

Reverse osmosis, in this context, is the process of water purification. This is done by placing a filter within your home water supply. This filter stops certain particles from continuing through your water supply. So they won’t reach your faucet.

The filter can remove a lot of particles. But this can often include minerals and vitamins that are actually good for you. So, there are a lot of benefits and drawbacks to reverse osmosis that need to be weighed up.

What is Not Removed by Reverse Osmosis?

Reverse osmosis does filter out quite a lot of contaminants. In fact, it filters out so many that it is difficult to say exactly what it cannot remove. As mentioned above, this can be a good and a bad thing.

This sometimes includes pesticides and other harmful chemicals. This isn’t always the case. The vast majority of contaminants are removed by reverse osmosis.

Reverse osmosis generally removes between 95% and 98% of all contaminants. There are some good alternatives. But reverse osmosis is one of, if not the, best water filtration system.

What Does Reverse Osmosis Filter Out?

So, now you know what reverse osmosis lets through, here are all the particles that reverse osmosis does remove.

  • Calcium
  • Chloride
  • Chromium
  • Copper
  • Fluoride
  • Lead
  • Magnesium
  • Nitrate
  • Phosphorous
  • Potassium
  • Radium
  • Sodium
  • Sulfate

Is Reverse Osmosis Bad For You?

This depends. There have been some reports by the World Health Organisation (WHO) which show the drawbacks of reverse osmosis. This is mostly due to the fact that reverse osmosis can filter out minerals that are actually good for you.

Water itself isn’t bad. In fact, as you likely already know, water should be an essential part of your diet. Water, whether drunk directly from the faucet or consumed through other food and drink, is essential for your overall health and wellbeing. (Interesting side fact: Humans can survive up to around 2 weeks without food. But only around 2 to 3 days without any water).

Of course, you will still be consuming water when you drink reverse osmosis water. But you won’t be getting all the benefits water usually provides.

This means that while reverse osmosis isn’t bad for you per se, it isn’t really good for you either. That is, unless you know for certain that your water contains harmful particles. In this case, reverse osmosis is better than consuming harmful substances.

If you have ever been under a Boil Water Advisory, then you will know the importance of purifying and filtering water. Reverse osmosis has been directly responsible for ending Boil Water Advisories. But, these have been in areas where the local water isn’t safe to consume.

So, don’t be tempted to install a reverse osmosis system as a way of bypassing using something like a water filter jug. Reverse osmosis is intended for situations where the water would otherwise be unsafe to consume and use.

Alternatives to Reverse Osmosis

So, if reverse osmosis doesn’t sound like it will work for your problem, what other methods can you use?

Ultrafiltration (UF) is one of the best alternatives. UF water is safe to consume and can remove around 99.99% of viruses and bacteria.

UF works by both filtering and disinfecting water. This is different from reverse osmosis which only provides a filter within the water supply.

That said, reverse osmosis does generally remove a higher number of contaminants. It’s important to seek local professional advice. This will give you a better understanding of the filtration needed for your specific water supply.

Another alternative to reverse osmosis is distillation. This is the process of heating the water to boiling point. The water vapors are then condensed and collected separately. The contaminants are left behind. And only the condensed water vapors come out of the faucet.

Do I Need a Reverse Osmosis System?

This is a really important question. A lot of people become immediately concerned about anything being in their water. This leads people to filter water as much as possible. A filtration jug is fine to make your water a little fresher.

But you only really need a reverse osmosis system if you’re really concerned about contamination. This should be severe contamination and not just the inclusion of certain minerals. Make sure to do some research into the water in your specific area. This will be a good way of determining whether you really need a reverse osmosis system.


What is not removed by reverse osmosis is minimal. It is actually generally intended for areas that do not have adequate filtration.

One reason why people invest in reverse osmosis systems is that they don’t believe the water in their local area is clean enough.

Truly harmful chemicals such as pesticides and herbicides can be removed to an extent. But reverse osmosis cannot remove everything. So, if you’re concerned about the cleanliness of your water, it’s worth considering other systems.

If you’re really concerned that your water isn’t safe, you should speak with your local representative.