Well water problems
Radon and uranium in well water: what the numbers mean and when to treat
The problem: a natural gas and a natural metal, both from the rock
Uranium occurs naturally in many rocks across the Piedmont and mountains of North Carolina. Radon is a gas produced as uranium breaks down, and it dissolves into groundwater. The state's 2009–2010 study traced the radon in sampled wells to uranium-rich minerals in that rock.[source] NC DHHS adds that these levels vary from neighbor to neighbor, that you can't smell, taste or see them, and that testing is the only way to know.[source]
Radon and uranium matter in different ways, so it helps to treat them as two separate questions.
Radon in water vs. radon in air
Most of the risk from radon in well water comes from breathing it, not drinking it. When you shower, run the dishwasher or do laundry, dissolved radon escapes into the air. The EPA says most of the risk from radon in water comes from that released gas, and that radon entering a home through the soil is usually a much larger risk than radon entering through water.[source] The state's 2011 study agrees that the risk from radon in water is generally small compared with indoor-air radon from soil and rock.[source]
North Carolina's rule of thumb: 10,000 pCi/L of radon in water adds about 1 pCi/L to the air in your home. The EPA's recommended level for indoor air is 4 pCi/L. That's why the NC Radon Program recommends testing your air first, then testing well water to see how much it contributes.[source]
What North Carolina recommends
| Radon in well water | State recommendation |
|---|---|
| 10,000 pCi/L or higher | Consider water treatment along with an air radon mitigation system. [source] |
| 4,000 to 10,000 pCi/L | Water treatment is optional. Use the result to judge whether water is a significant contributor to indoor air radon. [source] |
How common is it here?
The state sampled 115 wells (106 private, 9 community) across 18 western and central NC counties in 2009–2010, including Lincoln, Gaston and Catawba.[source]
1,010 pCi/L
median radon in 115 sampled NC wells
Higher in wells in granite-type (meta-igneous) rock.
14%
of those wells above 4,000 pCi/L
The proposed alternative level, never enacted.
1 of 37
wells above the 30 µg/L uranium standard
Uranium was detected in 41% of wells tested for it.
30%
of Piedmont and Blue Ridge wells sampled above 4,000 pCi/L radon
USGS, public-supply wells across 11 states.
Uranium data for counties close to Charlotte is thin. UNC's county tables tested very few wells for it here. In a 2019 Iredell County study of 786 homes, fewer than 2% of samples were above the EPA's health-based uranium standard.[source] If you're in Gaston, Lincoln or Iredell County, or anywhere on granite-type bedrock, it's worth adding to your test.
How testing works
Radon and uranium aren't on North Carolina's required new-well panel,[source] so most wells have never been tested for them. NC DHHS suggests that well owners in areas likely to have radionuclides start with a screen for:[source]
- Radon, which needs a special sampling technique because the gas escapes easily. Follow the lab's instructions exactly.
- Uranium, measured as a metal in µg/L.
- Gross alpha and gross beta, which screen for other radioactive elements, such as radium.
- Radon in your home's air, tested separately with an air test kit. North Carolina's Radiation Protection Section recommends testing the air in every home in the state.[source]
Not every lab is certified for these tests. NC DHHS keeps a list of state-certified labs.[source] We arrange the right panel through our well water testing service.
Treatment categories
Radon and uranium are treated differently. NC DHHS matches each to its own treatment types:[source]
| Contaminant | Treatment types listed |
|---|---|
| Radon | Aeration system; granular activated carbon; surface and decay storage [source] |
| Uranium | Ion exchange; reverse osmosis [source] |
| Radium | Ion exchange; reverse osmosis [source] |
- Radon calls for whole-house treatment. Because the risk comes from gas released at every tap and shower, EPA notes that point-of-use devices don't reduce the risk from breathing radon released throughout the home. Whole-house aeration or carbon is the usual approach.[source]
- Aeration vs. carbon. EPA says carbon filters usually cost less than aeration, but they collect radioactivity and may need special disposal.[source] Aeration needs venting to the outdoors and annual cleaning.[source] Which one fits depends on your level.
- Uranium is mainly a drinking-water question. Uranium matters in the water you drink, so certified reverse osmosis at the kitchen tap is a common option. Ion exchange is the whole-house alternative.
When to bring in a pro
If your air test is high, deal with the air first. The NC Radon Program can point you to air mitigation. If your water result is high, we'll help you weigh the state's recommendation against your air numbers. Whole-house radon systems tie into the main line and need venting or disposal planning. Here's how installation works.
Aeration units need periodic cleaning, and carbon or RO need scheduled changes. A Care Plan includes those plus retesting.
Questions we hear
Should I test my air or my water for radon first?
Your air. The NC Radon Program recommends an air test first, then a water test to see how much your well contributes. As a rule of thumb, 10,000 pCi/L in water adds about 1 pCi/L to indoor air.
Is there a legal limit for radon in well water?
No. EPA proposed limits for radon in water in 1991 and 1999, but neither was enacted, and private wells aren't regulated anyway. North Carolina's guidance suggests considering treatment at 10,000 pCi/L or higher, together with air mitigation.
Does a kitchen RO system take care of radon?
It doesn't address the main concern. Radon's risk comes mostly from gas released in showers and other household water use, which a single-tap system doesn't touch. RO is a reasonable option for uranium, which matters mainly in drinking water.
How worried should I be about radionuclides in my well?
Small amounts of natural radioactivity are everywhere in rock, soil and water. The real question is whether your levels are high enough to act on, and a lab test answers it. Most results lead to a simple decision, not an emergency.
Where we serve
Start with an honest answer about your water.
Tell us about your home and water source. We'll recommend testing first, and only the equipment your results support.