Groundwater in Cook County contains manganese, iron, nitrate, and sulfate at levels high enough to exceed EPA health standards. These contaminants are present at concentrations the EPA considers a concern, so well owners should test their water and consider treatment options.
These contaminants come from both natural and human sources in the area. Manganese and iron occur naturally when groundwater sits in contact with rock and soil that contain these metals. Nitrate and sulfate often enter groundwater from agricultural land, septic systems, and fertilizer use that is common across this region.
Groundwater in Cook County is hard, driven mainly by calcium and magnesium dissolved from the rock layers below. The surficial aquifer system here pulls these minerals from the surrounding geology as water flows through. Hard water is the norm across most wells in this county.
Wells in Cook County commonly contain iron, manganese, nitrate, and sulfate at levels above EPA health standards. Iron and manganese can cause serious problems with your blood and organs if you drink too much over time. Nitrate is especially dangerous for babies and pregnant women because it interferes with how the body carries oxygen. Sulfate in drinking water can cause digestive issues and other health problems.
The hard water in county wells leaves stains on sinks, showers, and laundry that are tough to clean. You might notice a metallic or unpleasant taste in your water. Scale builds up inside pipes and water heaters, which can reduce water flow and shorten the lifespan of appliances like dishwashers and water heaters over time.
We recommend testing your well water with a comprehensive panel to find out what is actually in your water, since every well is different and yours could have higher or lower levels than what is common in the county. Testing is the only way to know for sure what needs treatment. A comprehensive metals and minerals panel typically costs two hundred to four hundred dollars. Treatment options like iron filters or reverse osmosis systems can address multiple concerns at once.
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 ⓘ |
|---|---|---|---|---|---|
| Manganese | 20 | 25% | Moderate | High | |
| Sulfate | 42 | 14% | Moderate | Moderate | |
| Iron | 20 | 5% | Moderate | Moderate | |
| Nitrate | 41 | 2% | Moderate | Low | |
| Fluoride | 42 | 0% | Moderate | Low | |
| PFOA ⓘ municipal | 10 | 0% | Low | Safe | |
| Chloride | 48 | 0% | Moderate | Low | |
| Arsenic | 12 | 0% | Low | Low | |
| PFNA ⓘ municipal | 10 | 0% | Low | Safe | |
| HFPO-DA (GenX) ⓘ municipal | 10 | 0% | Low | Safe | |
| Nitrite | 18 | 0% | Moderate | Low | |
| Arsenic | 12 | 0% | Low | Low | |
| PFNA ⓘ municipal | 10 | 0% | Low | Safe | |
| PFOA ⓘ municipal | 10 | 0% | Low | Safe | |
| PFHxS ⓘ municipal | 10 | 0% | Low | Safe | |
| PFOS ⓘ municipal | 10 | 0% | Low | Safe | |
| Hardness | 42 | — | Moderate | Low | |
| Sodium | 42 | — | Moderate | Low | |
| pH | 43 | — | Moderate | Low | |
| PFBS ⓘ municipal | 10 | — | Low | Safe |
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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