Groundwater in Onslow County contains iron, chloride, and radon at levels that exceed health standards set by the EPA. These contaminants are present at concerning levels that well owners should know about and address.
Iron gets into your water from the rock layers below. The Castle Hayne formation that supplies your well contains iron-rich minerals that dissolve as water moves through the ground. Chloride can come from saltwater that has mixed into freshwater aquifers near the coast, or from road salt and other sources that have seeped down over time. Radon enters groundwater from natural radioactive minerals in the rock itself and cannot be prevented by what happens on the land surface.
Groundwater in this county is very hard, driven by high levels of iron, calcium, and magnesium from the rock below. The Castle Hayne formation releases these minerals as water flows through it. Most wells in Onslow County show this same hard-water character with elevated iron alongside the hardness.
Wells in Onslow County have three contaminants that exceed EPA health standards: chloride, iron, and radon. Chloride at elevated levels can raise blood pressure, especially in people who are sensitive to sodium. Iron above health standards can damage your organs over time. Radon is a radioactive gas that increases the risk of lung cancer when you breathe it in over many years.
The extremely hard water in county wells creates real problems in your home. You will see rust stains on your fixtures and in your bathtub or shower. Scale builds up inside pipes and on appliances, and hard water shortens the lifespan of water heaters and dishwashers. Your soap and detergent work poorly, so you use more of them and get less cleaning power.
We recommend testing your well with a comprehensive panel since multiple contaminants exceed health standards in this county. Every well is different, and your water could have higher or lower levels than what is common here. Testing is the only way to know what is actually in your well so you can treat it properly. A comprehensive metals and minerals panel costs between $200 and $400. Treatment options include water softeners for hardness and radon removal systems or aeration for the other contaminants.
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 ⓘ |
|---|---|---|---|---|---|
| Iron | 60 | 57% | Moderate | High | |
| Manganese | 50 | 18% | Moderate | High | |
| Chloride | 72 | 15% | Moderate | High | |
| Nitrate | 48 | 8% | Moderate | Moderate | |
| Sulfate | 70 | 3% | Moderate | Low | |
| Arsenic | 14 | 0% | Low | Low | |
| Fluoride | 59 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 22 | 0% | Moderate | Safe | |
| Lead | 22 | 0% | Moderate | Low | |
| Nitrite | 28 | 0% | Moderate | Low | |
| PFHxS ⓘ municipal | 22 | 0% | Moderate | Safe | |
| PFNA ⓘ municipal | 22 | 0% | Moderate | Safe | |
| PFOA ⓘ municipal | 22 | 0% | Moderate | Safe | |
| PFOS ⓘ municipal | 22 | 0% | Moderate | Safe | |
| Radon | 8 | 0% | Low | Low ⓘ | |
| Uranium | 14 | 0% | Low | Low | |
| E. coli | 1* | 0% | Low | Safe ⓘ | |
| Hardness | 70 | — | Moderate | Low | |
| PFBS ⓘ municipal | 22 | — | Moderate | Safe | |
| pH | 66 | — | Moderate | Low | |
| Sodium | 47 | — | Moderate | Low | |
| Total Coliform | 1* | 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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