Radon in Well Water
Radon is a radioactive gas from granite and other uranium-bearing rock. It leaves the water when you shower and joins the radon in your air, which is where the lung cancer risk is. Common in New England, the Appalachians, the Rockies and the Upper Midwest.
Likely causes
- Uranium decay in granite and metamorphic bedrock
- Deep bedrock wells in high-radon regions
Tests to order
- Radon in water
- Radon in air
- Uranium
- Gross alpha
Treatment options
- Aeration system vented outdoors
- Granular activated carbon for lower levels
- Home air mitigation
Water radon becomes air radon
Every 10,000 picocuries per liter of radon in water adds roughly 1 pCi/L to the air in the house, with showers and dishwashers doing most of the releasing. The EPA’s proposed guideline for water is 4,000 pCi/L, and some states use 2,000. Wells in granite country routinely test at 5,000 to 50,000. The health risk is from breathing it, not drinking it; drinking adds a small stomach cancer risk on top.
Test the water and the air together
A lab test for radon in water needs a special bottle with no air space, filled gently from a cold tap. Do a short-term air radon test in the lowest lived-in floor at the same time. If the air is high, you need air mitigation whatever the water shows. Add uranium and gross alpha to the water order, since the same rock that makes radon makes those.
Two ways to remove it
An aeration system bubbles air through the water in a sealed tank and vents the radon outside above the roofline, removing 95% or more, $3,500 to $6,000 installed. It is the right choice above about 5,000 pCi/L. Granular activated carbon in a large tank works for lower levels, is cheaper to buy, but the carbon becomes mildly radioactive over time and has to be handled at disposal. Point-of-use filters do nothing useful, because the exposure happens in the shower.
Is radon in water an emergency?
No. It is a long-term exposure risk. Test, then fix within months, not hours.
Does a softener or UV remove radon?
No. Only aeration or carbon does.