Groundwater in Onslow County contains iron, manganese, chloride, nitrate, and sulfate. These contaminants are present at levels that exceed EPA health standards and require your attention.
The Castle Hayne aquifer sits in rock that naturally holds these minerals and salts. Iron and manganese dissolve from the rock layers as water moves through them underground. Chloride and nitrate can also accumulate in this aquifer from both natural sources and human activity like agriculture and development in the area.
Groundwater in this county is hard, driven by elevated iron and manganese from the surrounding rock. The Castle Hayne aquifer's composition concentrates these metals as water filters down through the layers. Hard water with high iron and manganese is the norm for wells across Onslow County.
Onslow County wells commonly exceed EPA health standards for chloride, iron, manganese, nitrate, and sulfate. Elevated nitrate poses serious health risks, especially for infants and pregnant women, by interfering with oxygen transport in the blood. High levels of manganese can affect the nervous system and cause developmental problems in children. Iron and chloride at elevated concentrations also present health concerns over time with continued exposure.
The hard water in county wells creates noticeable quality-of-life problems. You will see rust-colored stains on fixtures, laundry, and plumbing. Hard water reduces soap effectiveness, leaves scale buildup in pipes and appliances, and can shorten the lifespan of water heaters and dishwashers. Some wells in the county produce water with a metallic or salty taste.
Testing is the only way to know what is actually in your well. Every well is different, and your water may have higher or lower levels than what is common across Onslow County. We recommend a comprehensive metals and minerals panel to check for all these contaminants, which typically costs between two hundred and four hundred dollars. Treatment options like iron removal systems and chloride reduction filters can address these issues once you know your specific water composition.
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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