Groundwater in Fairfax County contains manganese, radon, chloride, iron, lead, sulfate, and PFOA and PFOS. Several of these contaminants exceed EPA health standards and warrant attention.
The rock formations beneath Fairfax County naturally contain manganese and iron, which dissolve into groundwater as water moves through cracks and spaces in the stone. Radon comes from radioactive decay within that same rock. Chloride, lead, PFOA, and PFOS enter the groundwater from human sources: road salt spread on streets, lead in old plumbing and paint, and industrial or commercial chemicals that have seeped down into the aquifer.
Groundwater in this county is moderately hard, with elevated iron and moderate hardness driven by minerals dissolving from the bedrock. The early Mesozoic basin rock here releases these minerals as water percolates through it. Most wells in the county show these mineral characteristics, though individual wells can vary.
Wells in Fairfax County commonly exceed EPA health standards for chloride, iron, lead, manganese, PFOA, PFOS, radon, and sulfate. Lead damages the brain and nervous system, especially in children. Radon is a radioactive gas that increases lung cancer risk when inhaled over time. PFOA and PFOS are human-made chemicals that can harm the immune system and thyroid. Manganese at high levels affects the brain and nervous system. Chloride and sulfate at elevated levels can harm people with heart or kidney problems.
The moderate hardness and elevated iron in county wells create staining on laundry, dishes, and plumbing fixtures. A metallic or bitter taste in drinking water is common. Scale buildup inside pipes and appliances reduces water flow and shortens the lifespan of water heaters and dishwashers.
Your well is unique and may contain higher or lower contaminant levels than the county average. A comprehensive metals and minerals panel ($200-400) is recommended to see what is actually in your water so it can be treated properly. Iron filters and water softeners address mineral concerns, while activated carbon or reverse osmosis handle chemical 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 ⓘ |
|---|---|---|---|---|---|
| Manganese | 37 | 43% | Moderate | High | |
| Iron | 56 | 21% | Moderate | High | |
| PFOA ⓘ municipal | 44 | 20% | Moderate | High | |
| PFOS ⓘ municipal | 44 | 14% | Moderate | Moderate | |
| Sulfate | 56 | 4% | Moderate |
Moderate
Elevated concentration, not % above limit
|
|
| Nitrate | 54 | 2% | Moderate | Low | |
| Uranium | 31 | 0% | Moderate | Low | |
| Radon | 7 | 0% | Low | Low ⓘ | |
| PFNA ⓘ municipal | 44 | 0% | Moderate | Safe | |
| PFHxS ⓘ municipal | 44 | 0% | Moderate | Safe | |
| Nitrite | 54 | 0% | Moderate | Low | |
| Lead | 26 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 44 | 0% | Moderate | Safe | |
| Fluoride | 56 | 0% | Moderate | Low | |
| Sodium | 56 | — | Moderate | Low | |
| pH | 41 | — | Moderate | Low | |
| PFBS ⓘ municipal | 44 | — | Moderate | Low | |
| Hardness | 56 | — | Moderate | 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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