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Radon in water
How radon gets into water, who it affects most, how a water test differs from an air test, and how elevated water radon is treated.
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Radon water treatment: aeration and carbon systems compared
Short answer
A radon removal water system treats all the water where it enters the house, using either aeration, which mixes the water with air and vents the radon outdoors, or a granular activated carbon filter, which traps it. Typical radon reduction is 95 to 99 percent for aeration and 85 to 95 percent for carbon, which suits moderate levels of around 5,000 pCi/L or less.
Next step: find out how well water is tested and treated. Radon in water
Key takeaways
- Radon in water is removed at the point of entry, before water reaches the home's pipes, so radon is not released from any tap or shower.
- Aeration: typically 95 to 99 percent reduction, vents radon outdoors, needs annual cleaning; recommended for the highest levels.
- Granular activated carbon: typically 85 to 95 percent, best for moderate levels; the carbon collects radioactivity and may need special disposal.
- A filter at one tap, such as a drinking-water filter, does not reduce the radon released into the air from the rest of the water.
- Retest the water after the system is installed.
What a radon water treatment system does
A radon removal water system takes dissolved radon out of a home's water supply. If you have tested a private well and have a radon in water problem, it can be fixed, and the water can be treated in one of two ways, point-of-entry or point-of-use. Aeration and granular activated carbon filters are both straightforward and effective techniques for reducing radon in drinking water.
Typical radon reduction, EPA
Radon in private well water
- Private well water: aeration95 to 99 percentGenerally more efficient than GAC; requires annual cleaning to maintain effectiveness and to prevent contamination; requires venting radon to outdoors.
- Private well water: granular activated carbon (GAC)85 to 95 percentLess efficient for higher levels than aeration; use for moderate levels, around 5,000 pCi/L or less in water.
When radon water treatment is needed
There is no federal limit for private wells, so the decision rests on state guidance and your air result. In Vermont, a result at or above the 4,000 advisory level calls for action, and under it you do not need to treat. In Maine, 4,000 pCi/L is the point to weigh all your radon sources, treatment matters more as levels rise, and around 10,000 pCi/L you should strongly consider it.
| Result | Suggested treatment |
|---|---|
| 301 to 4,000 pCi/L | Treatment may be considered; a whole-house carbon system suits moderate levels |
| 4,000 to 10,000 pCi/L | Whole-house carbon or aeration; carbon suits levels around 5,000 pCi/L or less |
| Above 10,000 pCi/L | Whole-house aeration, which is generally more efficient; carbon is less efficient at higher levels |
Test the air too, before deciding how to reduce radon, because soil gas is usually the larger source. How results are read is on water testing.
Point of entry versus point of use
The line is clear. Point-of-entry treatment for the whole home removes radon before the water enters the home's distribution system, and usually uses granular activated carbon or aeration. Point-of-use devices remove radon at one tap and treat only a small portion of the water, such as the water you drink, so they are not effective against radon released into the air from all the water used in the home. The reason: radon can be released from water anywhere in the house, so it should be removed at or before the point the water enters.
| Device | Treats | Helps with radon in the air? |
|---|---|---|
| Whole-house aeration (point of entry) | All water entering the home | Yes, removes radon before it reaches any tap |
| Whole-house granular activated carbon (point of entry) | All water entering the home | Yes, removes radon before it reaches any tap |
| Point-of-use filter at a sink or tap | A small portion of the water, such as drinking water | No, not effective against radon released from all water used |
Radon aeration systems
Aeration strips radon out of the water with air. A typical system uses a fan, mixes the water with air inside a tank, and vents the air and radon outdoors away from the house. Some bubble air through the water; others draw the water into a holding tank, with the radon vented to the atmosphere.
| Feature | What to know |
|---|---|
| Typical reduction | 95 to 99 percent; up to 99% effective |
| Efficiency | Generally more efficient than carbon |
| Upkeep | Requires annual cleaning to keep working and prevent contamination |
| Venting | Requires venting radon to the outdoors |
| When recommended | Generally above 10,000 pCi/L |
| Installed cost, Georgia extension estimate | ~$4,000 installed |
Carbon filters usually cost less than aeration systems. An aeration system's fan uses electricity, so count operating costs, not only the purchase price.
Granular activated carbon (GAC) filters for radon
A carbon system is a filter tank on the incoming line. It traps radon on activated carbon surfaces until the radon decays, and the carbon has to be replaced on a schedule set by the radon level and other water quality factors. Install a carbon system certified to NSF/ANSI Standard 53.
| Feature | What to know |
|---|---|
| Typical reduction | 85 to 95 percent; more than 95% effective below 10,000 pCi/L |
| Best for | Moderate levels, around 5,000 pCi/L or less; not very effective above 10,000 pCi/L |
| Radioactivity | Radon by-products can build up on the carbon; a radiation shield around the tank and care in disposal may be needed |
| Where to put it | Outside the home or in an isolated area, because of that buildup |
| Upkeep | Carbon replaced regularly |
| Installed cost, Georgia extension estimate | ~$1,000 installed |
Aeration or carbon: how to choose
Both have advantages and disadvantages to discuss with your state radon office or a water treatment professional. Weigh the initial cost and the operating costs such as electricity, supplies and filters, repairs and maintenance, radon removal efficiency, life expectancy and warranty, and the manufacturer's reputation.
| Question | Aeration | Carbon (GAC) |
|---|---|---|
| Your level is above 10,000 pCi/L | Recommended | Not very effective |
| Your level is moderate | Works | Suited to around 5,000 pCi/L or less |
| Up-front cost | Higher; ~$4,000 installed | Lower; ~$1,000 installed |
| Radioactive waste | Radon vented outdoors | May need shielding and special disposal |
| Maintenance | Annual cleaning | Carbon replacement |
Home water treatment systems are not regulated by federal or state law, so look for systems certified by NSF International or the Water Quality Association, which generally assures a product performs as specified.
Radon water treatment cost
| System | Installed cost | Effectiveness |
|---|---|---|
| Aeration | ~$4,000 installed | Up to 99% effective |
| Granular activated carbon | ~$1,000 installed | More than 95% effective when radon is under 10,000 pCi/L |
These are approximate figures, not quotes for your house. Add the running costs, from electricity to filters and repairs. Some states help: Vermont offers funding to help pay for water treatment or to fix a water system, depending on eligibility; ask your own state's program.
After installation: maintenance and retesting
Retest the water
Retest after any treatment system is installed, to make sure levels are below the advisory level.
Keep up maintenance
Aeration needs annual cleaning; carbon needs regular replacement.
Keep a logbook
Record maintenance and repairs; no system works well unless maintained as the manufacturer recommends.
Plan disposal of spent carbon
Carbon filters can collect radioactivity and may require a special method of disposal.
Retest the air
Water treatment lowers the radon that comes from water only; test the air to see what remains from soil gas.
Radon water treatment questions
How do you remove radon from water?
With a whole-house system at the point of entry: aeration, or a granular activated carbon filter. See also how to get radon out of water.
Will an activated charcoal filter remove radon?
A whole-house granular activated carbon filter typically removes 85 to 95 percent and is best for moderate levels. A small filter at one tap does not address radon released elsewhere.
How does a radon aeration system work?
It mixes the water with air, often in a tank with a fan, and vents the air and radon outdoors away from the house.
How much does it cost to remove radon from water?
Georgia's extension service estimates about $4,000 installed for aeration and about $1,000 for carbon, plus running costs, as approximate figures.
Is aeration or carbon better for radon?
Aeration is generally more efficient and recommended at high levels; carbon costs less and suits moderate levels but collects radioactivity. Vermont discourages carbon for radon.
Does a water softener or reverse osmosis remove radon?
They are not the treatments health agencies name for radon, which are aeration and granular activated carbon at the point of entry.
What certification should a radon water system have?
NSF/ANSI Standard 53 for carbon systems, and in general NSF International or Water Quality Association certification.
Do I need to retest after installing a system?
Yes. Retest the water after any treatment system is installed.
Questions people ask
How do you remove radon from water?
Radon is removed from water with point-of-entry treatment, which treats all the water before it reaches the taps, usually by aeration, which typically removes 95 to 99 percent, or a granular activated carbon filter, which typically removes 85 to 95 percent. A filter at a single tap does not address radon released into the air.
What filters radon out of water?
For radon in indoor air, the recommended fix is not a filter: it keeps radon out, usually with a vent pipe and fan that pull it from under the house. For radon in well water, point-of-entry treatment works: a granular activated carbon filter typically removes 85 to 95 percent and aeration 95 to 99 percent.
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