Radon in Fresno County Water: Understanding Local Aquifer Levels and Treatment Capacity

You may have noticed occasional earthy or musty water taste or smell at your household taps in Fresno County and are aware radon can be present in local groundwater. Government samples taken from 36 wells in the Fresno County aquifer show radon levels ranging widely, from 114 to 6700 picocuries per liter (pCi/L), with a median of 640 pCi/L. These wells were 100 to 400 feet deep, but none exceeded the federal standard for radon in water. Knowing what this means for your household water is key.

How to judge treatment capacity against your household's daily water demand

When considering radon treatment, it’s important to assess how much water your household uses daily. Radon exposure through water primarily occurs by releasing radon gas into indoor air during water use, especially in showers, dishwashers, and washing machines. Treatment systems must handle the maximum flow rates of your home to be effective. The Fleck Radon in Water Filter ships ready to configure and can be sized based on your household’s typical daily water consumption, ensuring efficient radon reduction without wasting water or energy.

How to compare Fresno County's radon data with a neighboring county's without overreading it

Radon concentrations in groundwater vary greatly from place to place due to geology and depth of wells. The U.S. Geological Survey data specific to Fresno County's aquifer provides a snapshot of levels detected from December 2013 through April 2014 but should not be mistaken for individual well conditions. Comparing these numbers to those in a neighboring county can help understand regional trends but cannot substitute for testing your water. Differences in sampling methods, well depth, and geologic formations must be considered to avoid overinterpreting the comparison.

Why aesthetic secondary standards differ from health-based limits for radon

Radon is a radioactive gas naturally found in some groundwater sources. While the federal government sets a health-based maximum contaminant level for radon in drinking water, some aesthetic secondary standards exist for other constituents but do not apply to radon. These secondary standards relate to taste, odor, or staining and are not health-related. Radon’s main concern is its radioactivity and potential indoor air impact, not taste or appearance, so treatment focuses on reducing radon gas release from water rather than aesthetic effects.

What the measured radon range means against the federal standard, and what it does not mean

The USGS sampling in Fresno County found radon levels ranging from 114 to 6700 pCi/L with a median of 640 pCi/L. Importantly, none of these samples exceeded the federal maximum contaminant level (MCL) for radon. Detection indicates radon presence but does not imply an unsafe concentration or violation. Individual well water can differ widely, so these results provide context, not a diagnosis. The range shows radon is routinely detected here, so testing your water is the only way to know your household's specific level.

What distinguishes radon from the two water problems it is most often confused with

Radon differs from other potential water concerns such as dissolved gases causing odor or heavy metals causing staining. Unlike these, radon is a radioactive gas that primarily affects indoor air quality through water use. It cannot be detected by taste or visible signs in water. Its presence is confirmed only through specific laboratory testing. Understanding radon’s unique nature helps direct your focus toward appropriate testing and treatment options rather than misattributed causes for water issues.

The definitive step to assess your household water is ordering a certified radon test specifically for your well or water supply. This test reveals your water’s radon concentration, allowing informed decisions about mitigation. If radon is present at levels that warrant reduction, the Fleck Radon in Water Filter is proven to reduce radon effectively in residential water systems. It ships ready to configure, designed to treat the volume your household requires, helping reduce indoor radon exposure through water use.

Where this information comes from

Source: USGS groundwater sampling. Sampled 2014-04-08. 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 aquifer (Fresno County): 41 results from 36 wells, median 640.0 pCi/L, range 114.0-6700.0 pCi/L; none above any federal threshold