Should I test my well water for radon?
Yes, if your home uses a private well. EPA recommends testing private well water for radon (EPA). Radon dissolves into groundwater from rock, then escapes into the air when you shower, wash dishes or do laundry. City water drawn from lakes, rivers and reservoirs isn't a concern, and in most homes the soil under the house is a far bigger radon source than water.
Key facts
- On average only about 1–2% of indoor radon comes from water; most comes from soil (EPA).
- About 10,000 pCi/L of radon in water adds about 1 pCi/L to indoor air (Wisconsin DHS).
- EPA estimated radon in drinking water causes about 168 U.S. cancer deaths a year: about 89% lung cancer from breathing it, 11% stomach cancer from drinking it (EPA).
- There's no federal limit. EPA proposed one in 1999 but its archive still lists it as a proposal (EPA).
Who should test their water for radon?
- Homes on a private well. Drilled wells into bedrock are the main concern. Shallow dug or bored wells often don't reach water in contact with radon sources (UGA Extension).
- Neighbors can differ. Two wells close together can have very different radon levels, so a neighbor's result doesn't answer for your well.
- Homes on city water usually don't need a water test. If your utility uses groundwater rather than a lake or river, ask it about radon.
Test the air first with the free Tennessee kit, because soil is the main source. If you're on a private well, test the water too, especially if your air result is 4 pCi/L or higher (Wisconsin DHS).
How do I test well water for radon?
The free state kit measures air only, so well water needs a laboratory test.
- Find a lab that tests drinking water for radon. EPA suggests asking your state's laboratory certification office or state radon office for referrals (EPA). In Tennessee, call the Tennessee Radon Program at 1-800-232-1139, or the National Radon Helpline at 1-800-557-2366.
- Use the lab's sample container and instructions. Radon escapes from water quickly, so how the sample is collected and how fast it's mailed both matter.
- Sample from a tap that hasn't been through a radon treatment system, unless you're checking whether a system works.
What level of radon in water is a problem?
There's no federal limit. EPA's 1999 proposal for community groundwater systems used 300 pCi/L, or 4,000 pCi/L where a state runs a program to reduce radon in indoor air (EPA). This is how the University of Georgia's extension lab interprets private-well results:
| Radon in water | What it means |
|---|---|
| Below 300 pCi/L | Low. No treatment needed. |
| 300 to 4,000 pCi/L | Slightly elevated. Treatment may be considered. |
| 4,000 to 10,000 pCi/L | Significant. Whole-house carbon or aeration treatment recommended. |
| Above 10,000 pCi/L | Significant. Whole-house aeration recommended; also test for uranium and radium. |
Source: UGA Extension, Radon in Water.
How is radon removed from well water?
Treat the water where it enters the house, not at one faucet, because most of the risk comes from breathing radon released throughout the home (EPA).
| Aeration | Granular activated carbon (GAC) | |
|---|---|---|
| How it works | Bubbles air through the water and vents radon outside with a fan | A carbon tank captures radon from the water |
| How well it works | Up to 99% removal | Over 95% below 10,000 pCi/L; much less above that |
| Typical installed cost | About $4,000 | About $1,000, plus carbon replacement |
| Best for | Levels above 10,000 pCi/L | Levels below 10,000 pCi/L |
| Watch for | Fan and maintenance | Carbon collects radioactivity and may need special disposal; place the tank outside or in an isolated area |
Costs and effectiveness: UGA Extension. These are older Georgia estimates; get local quotes.
Home water treatment systems aren't regulated by federal or state law, so look for equipment certified by NSF International or the Water Quality Association (UGA Extension). Retest the water after the system is installed.
Does well water change my indoor radon test?
Only a little, unless the water is very high. At 10,000 pCi/L in water, water adds about 1 pCi/L to indoor air on average (Wisconsin DHS). If your air test is high, the soil is usually the main cause, and a soil-gas system is usually the first fix. See how radon mitigation works.
Where can I learn about other well-water problems in Tennessee?
Radon is one of many things worth testing a well for. Tennessee Water Authority, a separate website, publishes regional guides to iron, bacteria, nitrate, hardness and other well-water issues:
Frequently asked questions
Is it safe to drink well water with radon? Most of the risk comes from breathing radon released from the water, not drinking it. EPA estimated about 89% of the cancer deaths linked to radon in water are lung cancers from breathing it.
Will my regular water filter remove radon? Only a system designed for radon, such as aeration or a whole-house carbon tank, reliably removes it. Ask for the system's certification and retest after installation.
Does the free Tennessee radon kit test my water? No. It measures radon in the air only. Water needs a laboratory test.
Next step: Test your home's air for free →
Sources: EPA – Radon in drinking water Q&A (archive) · EPA – Radon in drinking water fact sheet (archive) · EPA – Proposed radon in drinking water rule (archive) · UGA Extension – Radon in Water (C 858-16) · Wisconsin DHS – Radon in Water · Tennessee Radon Program
Last reviewed October 22, 2026 by the Tennessee Radon Authority editorial team. How we research.