When people think about radon, they typically picture invisible gas seeping through a basement floor. But radon also dissolves into groundwater as it passes through uranium-containing rock formations. If your home relies on a private well, the water coming out of every tap could be carrying radon directly into your living space. For background on the issue, see our guide on radon in well water in Georgia.
1. How Radon Gets Into Well Water
Radon is produced when uranium in soil and rock undergoes radioactive decay. As groundwater flows through rock formations containing uranium, radon dissolves directly into the water. The amount depends on the uranium content of the surrounding rock and how long the water is in contact with it.
Bedrock Wells
Wells drilled into bedrock, particularly granite, tend to have the highest radon levels because the water has prolonged contact with uranium-bearing rock.
Shallow Wells
Shallow wells drawing from sand or gravel aquifers typically have lower radon levels, though exceptions exist where uranium-rich soil is present.
Once radon-laden water enters your home, the gas escapes into the air during everyday activities. Professional radon testing can measure both air and water levels. Showering, running the dishwasher, doing laundry, and even flushing toilets release radon from the water into your indoor air. The EPA estimates that water with 10,000 pCi/L of radon contributes roughly 1 pCi/L to indoor air levels.
2. Georgia's Geology and Well Water Radon
Georgia's geology creates a unique radon risk profile for well water users. The state's Piedmont region, stretching from the mountains to the fall line near Macon, sits on ancient metamorphic and igneous rock formations that are naturally rich in uranium.
Georgia Regions by Well Water Radon Risk
- North Georgia Mountains: Highest risk. Granite bedrock produces the most radon in groundwater. Wells here can exceed 20,000 pCi/L.
- Piedmont Region (Metro Atlanta north): High risk. Decomposed granite and gneiss formations commonly yield elevated radon levels in wells.
- Central Georgia: Moderate risk. Mixed geology with some areas of elevated uranium content.
- Coastal Plain: Lower risk. Sedimentary formations generally produce lower radon levels in groundwater.
3. Health Risks of Radon in Water
Radon in water creates two distinct exposure pathways, each with its own health implications.
Inhalation Risk (Primary Concern)
When radon escapes from water into indoor air, it becomes an inhalation hazard. This is the same risk pathway as soil-gas radon. Showers and hot water use release the most radon because agitation and heat accelerate gas release.
Ingestion Risk (Secondary Concern)
Drinking water containing radon poses a smaller but measurable risk of stomach cancer. The National Academy of Sciences estimates that radon in drinking water causes about 168 cancer deaths per year in the United States, primarily from stomach cancer.
4. How to Test Well Water for Radon
Testing well water for radon requires a different approach than testing indoor air. The sample must be collected carefully to prevent the radon from escaping before it reaches the laboratory.
Collect a "First Draw" Sample
The water sample should be collected from a cold water tap before any water has been used that day. This captures the highest radon concentration.
Use a Specialized Collection Kit
The sample vial must be filled underwater to prevent air exposure. Any bubbles in the sample will allow radon to escape and produce falsely low results.
Ship Immediately to the Lab
Radon has a half-life of 3.8 days. The sample must reach the laboratory quickly, ideally within 24 hours. Most testing companies provide overnight shipping labels.
Interpret Results
Results are reported in pCi/L. Action is generally recommended above 4,000 pCi/L. The EPA's proposed MCL of 300 pCi/L applies to public water systems, not private wells.
5. Treatment Systems for Radon in Water
Two proven technologies effectively remove radon from well water. Both are installed as point-of-entry systems that treat all water entering the home.
Aeration Systems
Aeration systems bubble air through the water, causing radon to transfer from the water into the air stream. The radon-laden air is then vented safely outside. These systems remove 95 to 99% of radon.
Cost: $3,000 to $5,000 installed
Best for: High radon levels (above 5,000 pCi/L)
Granular Activated Carbon (GAC)
GAC filters adsorb radon onto carbon granules as water passes through. Effective for moderate radon levels, but the carbon accumulates radioactivity over time and requires periodic replacement.
Cost: $1,000 to $3,000 installed
Best for: Moderate levels (below 5,000 pCi/L)
6. Radon in Air vs. Water: Understanding Both
It is important to understand that radon in well water and radon in indoor air are related but separate problems. Treating your water does not eliminate airborne radon from soil gas, and mitigating soil gas does not reduce radon in your water supply.
- Test both independently: High air radon does not predict high water radon, and vice versa. The sources and pathways are different.
- Address both if elevated: If both air and water tests come back high, you need both a sub-slab depressurization system and a water treatment system.
- Prioritize air first: The health risk from airborne radon (whether from soil or released from water) is much greater than the ingestion risk from drinking water.
7. When to Take Action
If you live in Georgia and rely on a private well, testing for radon in your water should be part of your regular water quality assessment. Here is a simple decision framework.
Action Steps for Well Water Users
- Test your well water if you live in North Georgia, the Piedmont region, or any area with granite bedrock
- If results are below 4,000 pCi/L, consider retesting every few years as conditions can change
- If results exceed 4,000 pCi/L, install a point-of-entry treatment system (aeration or GAC)
- Always test indoor air for radon separately, regardless of water results
Frequently Asked Questions
Concerned About Radon in Your Well Water?
If your home uses well water in Georgia, professional testing can determine whether radon treatment is needed. Contact us to learn more.
