Radon in Well Water: PA Homeowner Guide

Radon in well water is a serious but underrecognized problem in Pennsylvania. While most PA homeowners know about radon gas in basements, far fewer realize that the same radioactive element dissolves into groundwater — and enters your home every time you turn on a faucet or take a shower.

Pennsylvania has some of the highest radon levels in the United States. In certain counties, 67% of private wells show elevated radon concentrations. The Reading Prong geological formation stretching across the Lehigh Valley is a particular hotspot, but elevated levels appear statewide.

How Radon Gets Into Well Water

Radon is a naturally occurring radioactive gas produced by the decay of uranium in rock and soil. It dissolves easily into groundwater as that water moves through radon-producing formations underground.

When radon-contaminated water enters your home, the gas is released into indoor air through two main mechanisms. Showering and running hot water releases the most radon — the agitation and heat drive the dissolved gas out of solution. Washing dishes, doing laundry, and even flushing toilets contribute smaller amounts.

The EPA estimates that radon in well water contributes about 1% to 2% of total indoor radon exposure on average. But in homes with very high water radon levels and good air sealing, the contribution can be much higher.

Radon in Well Water: Where PA Risk Is Highest

Radon risk isn't uniform across Pennsylvania. Geological formations determine baseline levels.

Reading Prong (Lehigh Valley and Beyond)

The Reading Prong is a geological feature running from Connecticut through New Jersey and into Pennsylvania. It crosses Berks, Lehigh, Northampton, and parts of Bucks and Montgomery counties. The uranium-rich granitic rock produces extremely high radon levels in both air and water.

Wells drilled into the Reading Prong formation regularly show radon levels exceeding 10,000 pCi/L — far above any proposed standard. If your home is in this region, radon water testing is essential, not optional.

Piedmont and Central PA

The Piedmont region's metamorphic rock also produces elevated radon, though generally at lower levels than the Reading Prong. Central PA's limestone and shale formations vary widely. Some areas test low; others surprise homeowners with levels that warrant treatment.

Western PA

Western Pennsylvania generally has lower water radon levels, but localized hotspots exist. Granite outcrops and certain sedimentary formations in the Allegheny Plateau can produce moderate to high radon in groundwater.

Radon Water Testing in Pennsylvania

Testing is the only way to know your radon level. You cannot see, smell, or taste radon in water.

Radon water testing PA residents can access through several channels. Penn State Extension offers affordable test kits. PA DEP-certified labs accept mail-in samples. Local environmental testing companies provide on-site sampling.

The test itself costs $25 to $50 for water radon alone. Collection is straightforward but time-sensitive — radon dissipates from samples quickly, so you must follow the lab's instructions precisely and ship immediately after collection.

Understanding Radon Water Test Results

The EPA hasn't finalized a maximum contaminant level for radon in drinking water, but two proposed standards guide decisions.

• 4,000 pCi/L — proposed MCL for water systems that also have an indoor radon mitigation program (the "alternative MCL")
• 300 pCi/L — proposed MCL for water systems without indoor radon mitigation

Many PA wells exceed both thresholds. If your water tests above 4,000 pCi/L, treatment is strongly recommended. Between 300 and 4,000, consider treatment — especially if your home doesn't have a sub-slab depressurization system for airborne radon.

Radon Water Treatment Options

Two technologies effectively remove radon from well water.

Aeration systems are the most common and effective approach. These whole-house systems bubble air through the incoming water, stripping dissolved radon gas out of solution. The gas is then vented outside through a dedicated exhaust pipe. Aeration removes 95% to 99% of waterborne radon. Installation costs $2,500 to $5,000. Annual maintenance is minimal — typically a filter change and system check.

Granular activated carbon (GAC) filters also reduce radon effectively but come with a caveat. The carbon absorbs the radioactive radon, meaning the spent filter becomes radioactive waste. Filter replacement requires careful handling and proper disposal. GAC systems cost $1,000 to $3,000 installed, with filter replacement every 1 to 3 years at $200 to $500.

For most PA households with high water radon, aeration is the preferred choice. It doesn't concentrate radioactive material, requires less maintenance, and has a longer system life. Search our PA directory for water treatment companies that install radon removal systems.

PA County Radon Risk Levels in Well Water

Radon risk varies significantly across Pennsylvania's 67 counties. The following table shows the counties with the highest risk based on geological surveys and testing data from the PA DEP and Penn State Extension.

Risk Level	Counties	Primary Geology	Typical Water Radon (pCi/L)
Very High	Lehigh, Berks, Northampton, Chester, Montgomery	Reading Prong granitic rock	5,000–50,000+
High	Bucks, Lancaster, Delaware, York	Piedmont metamorphic	1,000–10,000
Moderate	Centre, Huntingdon, Mifflin, Columbia	Central PA limestone/shale	500–5,000
Low-Moderate	Allegheny, Westmoreland, Butler, Fayette	Allegheny Plateau sedimentary	100–2,000

These are general ranges — individual wells can vary dramatically even within the same county. A well drilled into a uranium-bearing granite vein may test at 30,000 pCi/L while a neighbor's well 500 feet away tests at 500 pCi/L. Geology at the wellhead depth is what matters, not the surface soil.

Treatment Cost Comparison: Aeration vs GAC

Choosing between aeration and granular activated carbon systems depends on your radon level, budget, and maintenance preferences. Here is a detailed cost comparison for radon water treatment options available to PA homeowners.

Factor	Aeration System	GAC Filter
Equipment + installation	$2,500–$5,000	$1,000–$3,000
Annual maintenance	$100–$200	$200–$500 (filter replacement)
10-year total cost	$3,500–$7,000	$3,000–$8,000
Radon removal rate	95%–99%	85%–99%
Best for radon levels	Any level (including very high)	Under 10,000 pCi/L
Radioactive waste	No — radon vented outdoors	Yes — spent carbon is radioactive
Space required	3 ft × 4 ft floor area	2 ft × 2 ft floor area
System lifespan	15–20 years	10–15 years (housing only)

For Reading Prong homeowners with water radon above 10,000 pCi/L, aeration is the only practical choice. GAC filters saturate too quickly at very high concentrations, requiring frequent and expensive filter changes. The spent carbon from high-radon wells also poses a greater disposal challenge because it accumulates more radioactive material.

For moderate radon levels (1,000 to 5,000 pCi/L), both technologies work effectively. GAC has a lower upfront cost, but the long-term expense of filter replacement can exceed aeration system costs over 10 years. Factor in the hassle of handling and disposing of radioactive filter media when making your decision.

Pennsylvania does not require a permit for installing radon water treatment systems, but the system must comply with local plumbing codes. Many counties in southeastern PA have licensed plumbers and water treatment specialists experienced with radon systems. Find qualified installers through our PA directory.

Radon Water Treatment: Maintenance and Long-Term Costs

Both aeration and GAC systems require ongoing maintenance to perform effectively. Neglecting maintenance can allow radon levels to creep back up without the homeowner knowing — the gas is invisible and odorless.

Aeration system maintenance: Annual inspection of the air pump, spray nozzles, and exhaust vent. Replace the air pump diaphragm every 3 to 5 years ($50 to $150). Clean the holding tank sediment every 2 to 3 years. Total annual maintenance cost: $100 to $200. Most PA water treatment companies offer annual service contracts that include testing to verify radon removal levels.

GAC filter maintenance: Replace carbon media every 1 to 3 years depending on water usage and radon concentration. Higher radon levels saturate the carbon faster, requiring more frequent replacement. Filter replacement costs $200 to $500 per change. Annual maintenance cost: $150 to $500 depending on replacement frequency. The spent carbon must be disposed of as low-level radioactive waste — your service provider should handle this as part of the replacement.

For both system types, retest your water 30 days after installation and annually thereafter to confirm continued radon removal. Testing costs $25 to $50 per sample through Penn State Extension or a certified lab. This annual test is your only way to know the system is still working since you cannot detect radon by taste, smell, or appearance.

Frequently Asked Questions About Radon in PA Well Water

Does radon in water cause cancer?

The primary risk from radon in well water is lung cancer — not from drinking the water, but from inhaling radon gas released into indoor air during showering and water use. The EPA estimates radon in drinking water causes about 168 cancer deaths per year nationwide, compared to 21,000 deaths from airborne radon.

Should I test my water if my basement radon test was low?

Yes. Low basement radon doesn't guarantee low water radon. They come from the same source (uranium decay in rock) but through different pathways. Your well may tap into a formation with high radon that doesn't affect the soil under your foundation, or vice versa.

How often should I retest my well water for radon?

Radon levels in well water are relatively stable because they're determined by geology rather than seasonal factors. One baseline test is typically sufficient unless you drill a new well, deepen your existing well, or install a treatment system. After installing treatment, retest to confirm the system is working correctly and bringing radon below your target level.

Can a whole-house carbon filter remove radon?

Yes, GAC filters remove radon effectively. However, the carbon accumulates radioactive material over time. This requires careful handling during filter changes and proper disposal of spent carbon. For homes with very high radon levels, aeration is generally preferred because it vents the radon gas outside rather than concentrating it in a filter.