Does Reverse Osmosis Remove Radon?

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Reverse osmosis is one of the best solutions for removing the majority of drinking water contaminants. But does reverse osmosis remove radon?

We’ve answered this question below.

📌 Key Takeaways:

  • Reverse osmosis doesn’t remove dissolved radon gas.
  • The carbon filtration stage of an RO system may reduce radon levels in water, but the radon particles will pass through the RO membrane.
  • The best alternative methods of removing radon are with a granular activated carbon filter and an aeration system.

🤔 What Is Radon?

It’s helpful to know a bit about radon and how it contaminates water before we move on.

Radon is a naturally occurring gas. It’s colorless and odorless, which means it’s impossible to detect it in your drinking water or your indoor air.

Radon is linked to numerous dangerous health effects, and may increase your risk of developing lung cancer, stomach cancer, and other life-threatening diseases. The Environmental Protection Agency (EPA) estimates that around 20,000 people die every year from inhaling radon gas in indoor air.

There is currently no legal maximum radon concentration in drinking water supplies, but the EPA has proposed a maximum contaminant level (MCL) of 300 pCi/L for this radioactive contaminant. Several states also have indoor air programs for radon.

Radon is rarely found in surface water, and isn’t usually a problem in city water supplies. People who own private wells are much more likely to be exposed to radon in the water.

How radon gets into water
source: Centers for Disease Control and Prevention

☣️ Does A Reverse Osmosis Filter Remove Radon?

No, a reverse osmosis system doesn’t remove radon.

The carbon filter stage in an RO system might reduce radon, but we don’t recommend relying on an RO system to eliminate this radioactive gas in your water.

Chances are, radon-contaminated water that has been treated with reverse osmosis will still contain this impurity.

🔎 How Effective Is Reverse Osmosis At Removing Radon Gas?

On a scale of 1 to 10, with 1 being “not effective at all” and 10 being “entirely effective”, a reverse osmosis system comes in at about a 3 for radon reduction.

The general consensus is that RO systems can’t remove dissolved gases, including radon gasses.

However, as we mentioned above, most RO units have an activated carbon filter, which can reduce radon. This limited amount of radon removal is why an RO system scores a 3 and not a 0 for its radon removal abilities.

🚱 Why Can’t A Reverse Osmosis System Remove Radon?

To understand why a reverse osmosis system can’t remove radon, we need to look at the RO process and what it’s intended to remove.

A reverse osmosis system has several stages of water filtration, including a sediment pre-filter, a carbon filter, a semipermeable membrane, and a post-filter.

Water is forced quickly through each of these filter stages. Each filter removes different sets of contaminants, and the RO membrane – the most important stage of the entire system – reduces up to 99% of total dissolved solids.

The RO membrane consists of tiny pores (from 0.1 to 5,000 nanometers, depending on the membrane design and complexity). To put this into perspective, a human hair is around 80,000 nanometers thick.

However, radon gas particles are incredibly small – around 0.5 to 3 nanometers. So, in an RO membrane with even a few pores larger than 3 nanometers, the radon gas particles will be small enough to slip through.

For that reason, RO can’t effectively be used for radon removal.

But what about the other filter stages?

It’s true that the activated carbon filter stage might reduce some radon in water, but the problem is that water is forced through the filter so quickly that there isn’t enough contact time for the radon to be effectively addressed.

Plus, the primary purpose of the carbon filter is to remove chlorine, preventing this chemical from damaging the semi-permeable membrane. It simply wasn’t designed to reduce drinking water radon, and its small size means that it’ll become clogged rapidly with this contaminant.

There are better solutions for removing radon that don’t have the setbacks of a reverse osmosis system.

Reverse osmosis membrane separation process
How the RO membrane works

🧐 Should You Use A Reverse Osmosis System To Remove Radon In Water?

You shouldn’t consider using a reverse osmosis system to remove radon from your drinking water.

The RO purification process isn’t effective at removing radon. Plus, RO systems cost a lot of money and require numerous filter changes per year. You might be willing to make the investment and commit to the maintenance time if the system was an effective method of radon treatment, but it’s not.

You can find other at-home water filters that do a much better job of reducing radon in the water, and they’re cheaper and easier to maintain, too.

In short, if you’re concerned about the radon levels in your water, don’t look to RO for guaranteed radon removal.

📑 Good Alternative Methods Of Radon Removal

So, what do we recommend instead of reverse osmosis systems to reduce your drinking water radon levels?

Granular Activated Carbon Filters

Granular activated carbon filters (GAC) use a process called adsorption to pull radon gas particles out of water.

The filter contains activated carbon particles, which trap the radon gasses and prevent them from re-entering the water supply.

You can find GAC filters that remove radon from your drinking water only (such as under-sink filters or water filter pitchers).

These are a great option if you have less than $100 to spend upfront and just want to avoid drinking radon in your water. However, we don’t recommend them if your water contains a lot of radon because their small size means they’ll get clogged rapidly.

If you want to also avoid radon exposure in the water you shower in, wash your clothes and dishes in, and use for all other purposes in your home, consider a point-of-entry GAC filter installed upstream of your hot water heater.

You’ll need more money upfront for a system like this – usually at least $350 for a cartridge system – but it’s still cheaper than other radon removal options.

Make sure you’re aware of how to safely dispose of your used GAC filter. Incorrect disposal may release radon gas back into the environment. You might also be concerned about the health risks associated with radon building up in the filter media over time.

Unboxing new black berkey filter elements

Aeration Systems

Our other top recommended method of reducing radon in your drinking water is an aeration system.

Aeration units send air bubbles through your water, which causes the radon gas particles to break down. The unit then carries these particles out of the water and releases them using a fan.

In an ideal scenario, an aeration system can reduce up to 99% of radon, making it the most effective technology for this purpose.

Aeration also has a one-up on carbon filtration because it doesn’t cause radon to accumulate inside the system, so you don’t have to worry about safe disposal. The radon is reduced before it even enters your home, so if you’re concerned about the health risks of breathing radon gas, an aeration system can make your indoor air much safer.

However, if your water contains high concentrations of manganese or iron, the effectiveness of the treatment method may be reduced.

Related Content: A Comprehensive Guide to Testing for Radon in Water


Can you remove radon by boiling water?

Yes, you can remove radon from your water by boiling it – but only to some extent. When water is heated and its temperature rises, radon gases become less soluble, causing them to escape from the liquid. This might effectively reduce the radon in the water, but it’s dangerous, since you’re at risk of numerous health effects if you inhale radon. It’s actually more dangerous to inhale radon in the air than it is to drink radon in the water.

What are the risks of radon exposure?

Radon exposure causes thousands of lung cancer deaths every year because radon particles get trapped in your lungs and accumulate over time. Radon may also cause other cancers, including stomach cancer.

How do you know if your water contains radon?

Water containing radon looks and smells like normal water, so you can only detect radioactive particles by conducting a radon water test. Since radon is such a dangerous contaminant, we recommend getting your water tested by a professional laboratory, which will give you the most accurate results and help you to take the appropriate action.

Water testing with tap score

Do any water filters remove radon?

Most standard water filters don’t remove radon, but one filter that can reduce this contaminant is a granular activated carbon filter. We recommend installing a point-of-entry GAC filter with a large surface area that can effectively trap high concentrations of this gas before it enters your whole home water supply.

Do water softeners remove radon?

No, water softeners don’t remove radon. They can only remove calcium and magnesium minerals, and low levels of iron and manganese – but no dissolved gases like radon. In fact, radon might accumulate in the softening tank and increase your risk of dangerous radon exposure in your home.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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