Radon in Well Water in Huntsville & Madison County: Testing and Treatment

Quick answer: Radon from soil is usually a much bigger risk than radon in water, according to the EPA. Test your indoor air first. If your home is on a private well, test the water too. Most of the risk from radon in water comes from breathing radon released during showers, laundry and dishwashing, not from drinking it. UGA Extension estimates that 10,000 pCi/L in water adds about 1 pCi/L to indoor air. If treatment is needed, use a point-of-entry system: granular activated carbon for lower levels, or aeration for levels of about 10,000 pCi/L and up.

Most homes in Huntsville and Madison get their water from a public utility. In the rural parts of Madison and Limestone counties, though, some homes still draw from a private well. Radon can dissolve in groundwater, so these homes have a second way for radon to get inside. This page explains how much that matters, how to test, and what the treatment options are.

How radon gets from a well into the air

The EPA's Citizen's Guide to Radon says there are two main sources of radon in indoor air: the soil and the water supply. Radon from the soil is usually a much larger risk than radon from water. Radon in water carries two risks. You can breathe it after it escapes from the water, and you can swallow it. The EPA says research shows the lung cancer risk from breathing radon is much larger than the stomach cancer risk from drinking it. Most of the risk from radon in water comes from radon released into the air when water is used for showering and other household tasks.

The Connecticut Department of Public Health makes the same point: radon escapes into the air during household water use, especially when the water is heated. Indoor levels rise for a short time when you run the dishwasher, washing machine, shower or bath. University of Georgia Extension estimates that 10,000 pCi/L of radon in water adds about 1 pCi/L to a home's indoor air. That ratio is why the air test still comes first.

Who should test the water?

Public water customers: The EPA says radon in water usually isn't a problem when the source is surface water. It's more likely when the source is groundwater, such as a private well or a public system that uses wells. If you're on public water and concerned, the EPA says to contact your water supplier.
Private well owners: Test the indoor air first. The EPA says that if the air test is high and the home has a private well, call the Safe Drinking Water Hotline at (800) 426-4791 for information on testing the water. Connecticut's health department goes further and recommends testing the water in every home on a well. It notes that water radon can be elevated even when indoor air is low.

Geology affects the odds. UGA Extension reports that, in its region, the highest radon-in-water levels come from wells in granite and other crystalline rock. Limestone aquifers are less of a concern there. Much of north Alabama is limestone karst, which ADPH notes makes air radon levels highly variable from house to house. No published survey tells you what a given Madison County well will show, so the only way to know is to test.

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How to test well water for radon

Water radon tests use a sample bottle that a certified lab analyzes. Radon escapes from water quickly, so follow the lab's instructions closely. Usually that means running the water first, filling the vial without bubbles, and shipping it promptly. Connecticut's health department bases its action recommendation on the average of two samples drawn at the same time from the same tap. It also notes that results vary with water use and seasonal changes in the water table, so a second round of testing is reasonable. UGA Extension recommends also testing for uranium and radium (gross alpha) when water radon is high, because those can be present too.

What the results mean

UGA Extension notes that no federal action level has been set for radon in drinking water. The states that publish guidance use their own numbers:

Connecticut DPH: recommends reducing radon in water when the two-sample average is 5,000 pCi/L or higher.
UGA Extension's lab: treats under 300 pCi/L as low, with no treatment needed. It calls 301 to 4,000 pCi/L slightly elevated, where carbon treatment can be considered. For 4,000 to 10,000 pCi/L it recommends carbon or aeration, and above 10,000 pCi/L it recommends aeration.

Whatever the water shows, UGA recommends testing the indoor air too and fixing the air if it's 4 pCi/L or higher. For most homes the soil, not the well, is the main source. Our radon health risk guide explains why the 4 pCi/L air number matters.

Treatment options

The EPA says a radon-in-water problem can be fixed in two ways. Point-of-entry treatment removes radon before water enters the house. Point-of-use devices treat water at one tap. They only treat a small share of the water you use and do little about radon released into the air from the rest. Both UGA and Connecticut recommend point-of-entry treatment. The two whole-house options are:

Granular activated carbon (GAC): a tank of carbon traps radon as water passes through. UGA puts it at over 95% effective below 10,000 pCi/L, with installed costs around $1,000. Connecticut cites an average of $1,500 to $3,500. The carbon has to be replaced on a schedule. Radioactive decay products can build up in it, so UGA suggests placing the unit outside the home or in an isolated area, and spent carbon may need special disposal.
Aeration: air is bubbled or sprayed through the water and the radon is vented outdoors. UGA says aeration can be up to 99% effective and costs about $4,000 installed. Connecticut calls it the only effective method at or above 10,000 pCi/L.

UGA advises comparing operating costs, maintenance, removal efficiency, warranty and the maker's reputation. It also suggests looking for NSF International or Water Quality Association certification, because home water treatment equipment isn't regulated by federal or state law. Connecticut recommends having a nationally certified radon professional install the system.

Air and water together

If both the air and the water are high, they're usually handled separately. A soil suction system lowers the air level, and a point-of-entry unit treats the water. Fix the air first in most cases, because that's where most of the risk is. Then retest the air once the water system is running. We handle the air side across Madison and Limestone counties (see our mitigation systems guide). If your well needs treatment, we can tell you what to ask a water treatment installer.

Frequently asked questions

Is radon in well water dangerous to drink?

Swallowing radon carries a small stomach cancer risk. The EPA says the much larger risk is breathing radon that escapes from water during showers and other household use.

How much does radon in water raise indoor radon?

UGA Extension estimates that 10,000 pCi/L in water adds about 1 pCi/L to indoor air. Soil gas is usually the bigger source, so test the air too.

Is there a legal limit for radon in private well water?

No. UGA Extension notes there's no federal action level for radon in drinking water. Some states publish guidance, such as Connecticut's 5,000 pCi/L action level.

Will a filter on my kitchen faucet fix it?

No. The EPA says point-of-use devices treat only a small share of your water and don't reduce radon released into the air from showers and laundry. Use a point-of-entry system.

Should I test my water if I'm on Huntsville city water?

Usually test the air first. If you're concerned about the water, the EPA says to contact your water supplier, since radon in water is mainly an issue with groundwater sources.