Testing and Mitigating Arsenic and Radon in Well Water
For the roughly 43 million Americans who rely on private wells, the water flowing into their homes can feel like a direct gift from the earth—until testing reveals invisible threats like arsenic and radon. These naturally occurring contaminants are among the most common and serious risks in private well water across the United States, and unlike municipal supplies, no one is required to treat them for you. The responsibility falls entirely on the homeowner. The good news is that both arsenic and radon are detectable with straightforward testing and manageable with proven, often surprisingly affordable technologies.
Arsenic in well water has quietly become one of the biggest public health stories most people have never heard. The EPA classifies arsenic as a human carcinogen, linking long-term exposure—even at low concentrations—to skin lesions, cardiovascular disease, diabetes, and multiple forms of cancer, including bladder, lung, and skin. Maine, New Hampshire, Michigan, and large swaths of the Southwest routinely show bedrock wells exceeding the federal Maximum Contaminant Level (MCL) of 10 parts per billion (ppb). In some New England counties, more than 30 percent of wells test above that threshold.
Radon, a colorless, odorless radioactive gas, presents a different but equally insidious risk. It enters well water by dissolving out of uranium-bearing granite and other bedrock. When the water is agitated—showers, dishwashers, laundry—the radon is released into household air. The EPA and Surgeon General rank radon as the second-leading cause of lung cancer in the United States, behind smoking. In high-radon states like Iowa, Pennsylvania, and much of New England, indoor air contributions from well water can push total radon exposure well above the EPA action level of 4 picocuries per liter (pCi/L) in air. A well containing 10,000 pCi/L of radon in water can add 1 pCi/L to indoor air for every 10,000 pCi/L in the water—a simple but alarming 10,000-to-1 rule of thumb.
The first and non-negotiable step for any private well owner is testing. You cannot taste, smell, or see either contaminant. Waiting until you have symptoms is not an option.
Testing for Arsenic
Most state health departments and certified laboratories offer mail-in arsenic test kits for $20–$40. The sample must be collected in a special bottle with a preservative acid (usually provided) and kept cool until it reaches the lab. Results are reported in micrograms per liter (µg/L), equivalent to parts per billion. Anything above 10 µg/L requires action; many oncologists and toxicologists now recommend treating at 5 µg/L or lower because there is no known safe threshold for a carcinogen.
Testing for Radon in Water
Radon testing requires even more care to prevent the gas from escaping the sample before analysis. Labs provide a small vial and strict instructions: collect the sample with no aeration, fill it completely underwater, and ship overnight. Costs range from $75–$150 depending on the lab. The EPA has not set an MCL for radon in drinking water, but proposes a range of 300–4,000 pCi/L depending on whether a community has an active indoor air mitigation program. Most experts recommend treatment below 2,000 pCi/L, and many homeowners aim for under 1,000 pCi/L when children or former smokers are in the home.
How often should you test? At minimum, test for arsenic once when you move in and again every five years, or immediately if you notice changes in water taste, staining, or nearby drilling activity. Test radon in water whenever you test indoor air radon, or at least every five years. Seasonal fluctuations can occur, with radon often higher in winter due to closed houses and lower well recharge.
Mitigating Arsenic
Once arsenic is confirmed, three treatment technologies dominate the residential market:
Adsorptive media (usually iron-based or titanium-based media) that bind arsenic as water passes through a tank. These are point-of-entry (whole-house) systems and the most common choice for levels up to 100–150 ppb.
Reverse osmosis run at the point of use (typically under the kitchen sink) for drinking and cooking water only. RO removes 95–99 percent of arsenic but wastes water and does not protect showers or laundry.
Anion exchange systems, which work like a water softener but swap chloride for arsenate ions. Less common for homes because they create a brine waste stream.
Whole-house adsorptive systems are generally the gold standard for families who want every tap protected. Properly sized tanks with certified media can last 3–10 years before replacement, depending on water chemistry and volume used.
Mitigating Radon
Radon removal is remarkably effective and, in most cases, less expensive than arsenic treatment. Two methods account for nearly all residential installations:
Aeration (also called spray aeration or packed-tower aeration): Water is sprayed or cascaded through a sealed tank while a fan pulls air across it, venting radon safely outside. Removal rates exceed 99 percent even at very high starting levels.
Granular activated carbon (GAC): Radon adsorbs onto large carbon contact tanks. While effective, GAC accumulates radioactivity over time and must be handled as low-level radioactive waste upon replacement, making aeration the preferred choice for most homes.
A well-designed aeration system installed by a competent water treatment professional typically costs $2,500–$4,500 and adds almost no operating expense beyond a small blower fan.
The Role of Storage Tanks and the Well Harvester®
Many homeowners facing arsenic or radon issues also struggle with low-yield or shared well situations that make conventional treatment challenging. Continuous-flow treatment systems assume the well pump can deliver a steady 8–12 gallons per minute. When a well recovers at only 0.5–2 GPM—or when multiple households draw from a shared well—those treatment systems either sit idle waiting for enough flow or force the well pump to short-cycle and burn out.
This is where atmospheric storage paired with a dedicated booster pump becomes transformative. By harvesting whatever the well can safely produce into large FDA-approved tanks and then repressurizing on demand, homeowners gain two critical advantages: they protect the well from over-pumping, and they create the consistent high flow that treatment systems require.
The Well Harvester from Epp Well Solutions exemplifies this approach. Unlike traditional pressure tanks that hold only 20–80 gallons, the Well Harvester automatically fills one or more 215-gallon storage tanks only as fast as the well can recover, using patented sensors to prevent any chance of overpumping damage. When a faucet opens, the system instantly delivers 20 GPM of treated, high-pressure water regardless of the well’s native yield. Homeowners with arsenic adsorptive systems or radon aeration towers upstream of the storage tanks will find that the Well Harvester eliminates short-cycling, extends media life, and ensures every gallon receives full treatment contact time. In shared well agreements where neighbors once argued over pump run times, the abundant stored volume removes contention entirely.
Installation is straightforward: the Well Harvester sits between the treatment equipment and the well pump. Its digital interface displays real-time harvested gallons, well harvedt rate, and system status, giving owners unprecedented insight into their water supply.
Practical Steps for Homeowners
If you’re on a private well and have never tested for arsenic or radon, order both tests this month. Most state labs or certified private labs can process them quickly. While waiting for results, locate your wellhead, note its depth and static level if known, and inventory how many gallons per minute you actually get when multiple fixtures run. That baseline data will prove invaluable when choosing treatment.
Once results return, work with a water professional who understands both contaminant removal and low-yield dynamics. In many cases, combining proven treatment (adsorption for arsenic, aeration for radon) with intelligent storage like the Well Harvester creates a solution that is more reliable, longer-lasting, and ultimately less expensive than repeatedly replacing burned-out pumps or drilling new wells.
The earth beneath your property may have delivered arsenic or radon along with your water, but modern science has given homeowners the tools to send those threats safely on their way—often for far less than the cost of a single emergency pump replacement. Testing is the first step; informed treatment is the lasting answer. Your family’s health, and the longevity of your well, are worth the effort.
