Well water in Fairfax County, Virginia
In Fairfax County, 2% of 65 tested well samples exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
529 test results across 13 contaminants from at least 34 wells, 1976 to 2025; nitrate has the most at 65. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 4 people in Fairfax County get their drinking water from a private well, per USGS 2015 county water use. That is about <1% of residents.
Separately, the USGS national arsenic model estimates that 100% of the 4 people on private wells in Fairfax County draw water above 10 ug/L, from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Fairfax County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Nitrate 1976 to 2025 | 65 | 89% | 0.56 | 14 | 10 mg/L EPA limit | |
| Fluoride 1976 to 2025 | 65 | 77% | 0.07 | 1.1 | 4 mg/L EPA limit | |
| Uranium 1994 to 2025 | 40 | 60% | 0.053 | 0.406 | 30 ug/L EPA limit | |
| Arsenic 1998 to 2025 | 35 | 46% | 0 | 0.8 | 10 ug/L EPA limit | |
| Copper 1998 to 2025 | 32 | 47% | 0 | 0.162 | 1.3 mg/L EPA limit | |
| Lead 1998 to 2025 | 32 | 25% | 0 | 6.73 | 15 ug/L EPA limit | |
| Chloride 1976 to 2025 | no limit | 65 | 100% | 11.8 | 209 | 250 mg/L nuisance level |
| Sodium 1976 to 2025 | no limit | 65 | 100% | 13.8 | 159 | 20 mg/L health guideline |
| Iron 1976 to 2025 | no limit | 65 | 88% | 50 | 10,700 | 300 ug/L nuisance level |
| Manganese 1976 to 2025 | no limit | 46 | 96% | 38.5 | 813 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (8), E. coli (4), Radon (7).
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 4%28 samples | 0%16 samples | 0%12 samples | n/a |
| Fluoride | 0%28 samples | 0%16 samples | 0%12 samples | n/a |
| Uranium | n/a | 0%12 samples | 0%12 samples | n/a |
| Arsenic | n/a | 0%12 samples | 0%12 samples | n/a |
| Copper | n/a | 0%12 samples | 0%12 samples | n/a |
| Lead | n/a | 0%12 samples | 0%12 samples | n/a |
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
The contaminants most often above their limit here are nitrate (2% of 65 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Fairfax County
- 1Nitrate2% of 65 local samples were above the limit.
- 2Coliform bacteriaRecommended for every private well, every year.
- 3RadonMedian local reading is 1,200 pCi/L.
- 4ChlorideDetected in 100% of local samples.
- 5ManganeseDetected in 96% of local samples.
- 6IronDetected in 88% of local samples.
- 7FluorideDetected in 77% of local samples.
- 8Volatile organic compounds (VOCs)3,863 leaking underground storage tank sites on record locally.
Test your Fairfax County well for nitrate, coliform bacteria and radon
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Virginia: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Fairfax County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Fairfax County
Piedmont and Blue Ridge crystalline-rock aquifers
Igneous and metamorphic-rock. Granite and similar crystalline rock hold water only in fractures. Wells are deep and yields modest, and the rock itself is the source of arsenic, radon and uranium, which is why those three head the test list in bedrock country.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Virginia
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Private Well Program, VDH
- Drinking Water Laboratories, Virginia DCLS
Contamination sources on record in Fairfax County
Virginia DEQ records 3,863 leaking underground storage tank sites and 62 reported spills and releases in Fairfax County, among 3,961 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 3,863
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 62
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 14
- lined landfills and transfer facilities
- 22
- other solid waste facilities
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
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Common questions
Is there arsenic in well water in Fairfax County?
Arsenic was detected in 46% of 35 public well samples in Fairfax County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How often should I test a private well in Fairfax County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Counties near Fairfax County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Virginia dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 529 samples in Fairfax County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 4 people on private wells in Fairfax County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Virginia DEQ regulated sites: 3,961 regulated sites located in Fairfax County. Petroleum releases and solid waste permits from the Virginia Department of Environmental Quality Environmental Data Mapper. Retrieved September 17, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.