Oswego County well owners should be aware of radon, manganese, iron, arsenic, and chloride in their groundwater. Several of these contaminants exceed EPA health standards and warrant attention.
These contaminants come from the limestone and carbonate rock beneath the county. Radon and arsenic occur naturally in the rock itself. Manganese and iron leach into water as it filters through the carbonate minerals. Chloride can accumulate from both natural sources and surface activities like road salt application.
Groundwater in this county is hard, driven by calcium and magnesium that dissolve from the limestone bedrock as water moves through it. This character is common across wells throughout Oswego County because the carbonate rock naturally releases these minerals into the water. Elevated hardness appears in most wells tapping this aquifer.
Wells in Oswego County commonly contain arsenic, chloride, iron, manganese, and radon at levels that exceed EPA health standards. Arsenic can damage organs and increase cancer risk over time. Radon is a radioactive gas that enters the lungs and raises the risk of lung cancer. Manganese at elevated levels can affect the nervous system. Chloride and iron above health limits can cause problems with organs and tissues.
The county has hard water, which creates scale buildup inside pipes and water heaters. You might notice rust-colored or brown staining on sinks, tubs, and laundry. Some people detect a metallic taste in their water. Hard water can shorten the lifespan of appliances like dishwashers and water heaters because scale reduces their efficiency.
We recommend testing your well with a comprehensive metals and minerals panel, since multiple contaminants exceed health standards. Every well is different, and yours may have higher or lower levels than what is common in the county. Testing is the only way to know what is actually in your water so it can be properly treated. Depending on your results, treatment options like water softeners, radon aeration systems, or iron filters can help address specific concerns.
Not sure if your well is affected? Get certified results in 5–7 days.
Test Your Well Water with Tap Score →| Contaminant | Samples ⓘ | % Above MCL ⓘ | Distribution ⓘ | Confidence ⓘ | Risk ⓘ |
|---|---|---|---|---|---|
| Radon | 20 | 70% | Moderate | High ⓘ | |
| Manganese | 96 | 33% | Moderate | High | |
| Iron | 96 | 18% | Moderate | High | |
| Chloride | 96 | 5% | Moderate | Moderate | |
| Arsenic | 38 | 3% | Moderate | Low | |
| Fluoride | 96 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 16 | 0% | Moderate | Safe | |
| Lead | 38 | 0% | Moderate | Low | |
| Nitrate | 34 | 0% | Moderate | Low | |
| Nitrite | 31 | 0% | Moderate | Low | |
| PFHxS ⓘ municipal | 16 | 0% | Moderate | Safe | |
| PFNA ⓘ municipal | 16 | 0% | Moderate | Safe | |
| PFOA ⓘ municipal | 16 | 0% | Moderate | Safe | |
| PFOS ⓘ municipal | 16 | 0% | Moderate | Safe | |
| Sulfate | 96 | 0% | Moderate | Low | |
| Uranium | 29 | 0% | Moderate | Low | |
| E. coli | 6* | 0% | Low | Safe ⓘ | |
| Fecal Coliform | 7* | 0% | Low | Low ⓘ | |
| Hardness | 99 | — | Moderate | Low | |
| PFBS ⓘ municipal | 16 | — | Moderate | Safe | |
| pH | 99 | — | Moderate | Low | |
| Sodium | 96 | — | Moderate | Low | |
| Total Coliform | 7* | 0% | Low | Low ⓘ |
MCL = Maximum Contaminant Level (EPA limit for public water; used as benchmark for private wells). Distribution shows % of sampled wells in each concentration band. Methodology.
* Microbial contaminants (E. coli, coliform) reflect only samples from the last 10 years.
Data shows potential risk — a certified test confirms whether your water is affected.
Order a Tap Score Test →Population-level CDC data. Not individual risk prediction.
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