How do public-system radon records differ from private-well testing in what they establish?
Public radon data for groundwater in Pima County come from government sampling of wells in the regional aquifer known as N100BSNRGB. These samples were taken from six wells ranging between 300 and 800 feet deep, between June and September 2013. While these records show radon was detected in all samples, this information only reflects the aquifer's general condition and does not reveal radon levels in any individual household's water. To understand radon concentration in your own well water, you need a certified laboratory test of a current sample from your specific water source. Without that test, area measurements provide context but not an exact measurement of your water quality.
What happens when radon in water is left untreated for years?
Radon is a naturally occurring radioactive gas that can dissolve into groundwater from surrounding rock formations. Over time, radon in water contributes to indoor air radon levels when water is used for showering, cooking, and cleaning. Prolonged exposure to elevated radon levels is linked by health authorities to lung cancer risk, primarily through inhalation of radon released into the air. A household system that cannot keep up with radon reduction may allow increased radon exposure indoors, especially over many years. Addressing radon in water reduces one source of indoor radon, complementing radon mitigation efforts for soil gas.
How can a homeowner interpret the median and range of radon levels found in Pima County wells?
The government samples in Pima County recorded radon levels from 175 to 1410 picocuries per liter (pCi/L), with a median value of 1100 pCi/L. These figures mean that half of the sampled wells had radon above 1100 pCi/L, and half below, and that the lowest and highest detected values were 175 and 1410 pCi/L, respectively. None of these measurements surpassed any federal health-based thresholds. This range shows that radon presence in the aquifer can vary significantly by location and well depth, but these numbers alone do not determine your household's radon level. If your system seems overwhelmed, the concentration in your water might be near or above this range, but only individual testing can confirm this situation.
What household symptoms suggest radon in water is a concern, and which do not?
Radon in water itself does not change water taste, odor, color, or cause common water stains. Unlike some other contaminants, you will not notice radon by sensory changes. Symptoms that could indicate radon as a water issue include persistent indoor radon readings despite soil-focused mitigation and water treatment systems operating below capacity. Conversely, respiratory symptoms, skin irritation, or plumbing issues typically are unrelated to radon. If your household radon mitigation equipment struggles to reduce radon below target levels, it signals a need to reassess your water treatment solution, not that radon is causing physical water problems.
What does a certified radon-in-water laboratory test report, and how should it be read?
A certified laboratory test for radon in water reports the concentration in picocuries per liter (pCi/L), providing a specific measurement for your sample. This figure is the only way to know your well water's exact radon level and to track changes over time. Evaluating that result against federal or state guidelines helps determine if additional treatment is advisable. Since radon is a gas, test results reflect recent water conditions and may vary seasonally or with well usage. Keeping a record of tests ensures informed decisions about your household's radon reduction needs.
For households in Pima County whose current radon mitigation equipment cannot keep up, the Pentair Radon in Water Filter offers a direct-purchase option designed to handle the demand indicated by your test results. This system ships ready to configure, providing an effective strategy for reducing radon concentrations in residential well water.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2013-09-04. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.
On record: U.S. Geological Survey sampling of Radon-222 in the N100BSNRGB aquifer (Pima County): 6 results from 6 wells, median 1100.0 pCi/L, range 175.0-1410.0 pCi/L; none above any federal threshold