Well water in Orange County, North Carolina
In Orange County, 3% of 7,286 private wells tested between 1998 and 2019 had lead above the North Carolina groundwater standard (15 ug/L), according to the NC State Laboratory of Public Health (NCWELL).
The strongest signal is E. coli: 18% of 50 local samples were above the limit, too few samples to carry the headline but first on the test list below.
7,286 private wells tested 1998 to 2019 in state summaries; 885 test results across 13 contaminants from at least 70 wells, 1950 to 2013; nitrate has the most at 165. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 37,751 people in Orange County get their drinking water from a private well, per USGS 2015 county water use. That is about 27% of residents.
Separately, the USGS national arsenic model estimates that 7% of the 37,751 people on private wells in Orange County draw water above 10 ug/L (the model's range is 4% to 14%), from geology and well depth rather than local tests.
What homeowner tests found
NCWELL private well summaries: private wells tested and reported to the state, 1998 to 2019. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
What individual samples found
Each row summarizes every public sample for that contaminant inside Orange 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 |
|---|---|---|---|---|---|---|
| E. coli 2007 to 2013 | 50 | 18% | 0 | 52 | 0 MPN/100mL EPA limit | |
| Nitrate 1950 to 2013 | 165 | 88% | 0.782 | 31.9 | 10 mg/L EPA limit | |
| Fluoride 1950 to 2013 | 112 | 65% | 0.055 | 0.6 | 4 mg/L EPA limit | |
| Lead 1998 to 2007 | 33 | 30% | 0 | 4 | 15 ug/L EPA limit | |
| Copper 1998 to 2007 | 33 | 61% | 0.001 | 0.024 | 1.3 mg/L EPA limit | |
| Arsenic 1998 to 2007 | 33 | 21% | 0 | 4 | 10 ug/L EPA limit | |
| Chloride 1950 to 2013 | no limit | 112 | 100% | 5.55 | 81 | 250 mg/L nuisance level |
| Sodium 1950 to 2013 | no limit | 112 | 100% | 7.68 | 40.5 | 20 mg/L health guideline |
| Iron 1950 to 2013 | no limit | 112 | 79% | 4.65 | 2,000 | 300 ug/L nuisance level |
| Manganese 1950 to 2007 | no limit | 64 | 95% | 5 | 890 | 300 ug/L health guideline |
| Radon 1998 to 2007 | no limit | 53 | 100% | 400 | 4,460 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (4), Uranium (2).
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 | 2%113 samples | n/a | 23%48 samples | n/a |
| Fluoride | 0%62 samples | n/a | 0%48 samples | n/a |
Nitrate above the limit in Orange County rose from 2% of 113 samples before 2000 to 23% of 48 in the 2010s.
Fluoride has held within a few points between the two most recent periods with enough samples.
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
Among homeowners in Orange County who sent a sample to the state lab, the health-based limits most often exceeded were lead (3% of 7,286 wells), arsenic (1% of 7,262 wells), and copper (<1% of 3,582 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
Manganese and iron exceed the state's advisory level in a sizable share of wells; these are mostly a taste, staining or diet issue rather than a toxicity one.
What to test for in Orange County
- 1E. coli18% of 50 local samples were above the limit.
- 2Nitrate8% of 165 local samples were above the limit.
- 3Lead3% of 7,286 local wells tested were above the North Carolina groundwater standard.
- 4Arsenic1% of 7,262 local wells tested were above the North Carolina groundwater standard.
- 5Copper<1% of 3,582 local wells tested were above the North Carolina groundwater standard.
- 6RadonMedian local reading is 400 pCi/L.
- 7Manganese30% of 7,250 local wells tested were above the North Carolina groundwater standard.
- 8Iron22% of 3,557 local wells tested were above the North Carolina groundwater standard.
- 9Volatile organic compounds (VOCs)743 leaking underground storage tank sites on record locally.
Test your Orange County well for E. coli, nitrate and lead
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 North Carolina: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Orange County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Orange 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 North Carolina
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 Water Testing FAQs, NCDHHS
- NCSLPH - Lab Certification, NCDHHS
Contamination sources on record in Orange County
NC DEQ records 743 leaking underground storage tank sites in Orange County, among 743 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.
- 743
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
Treatment that fits the local profile
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
E. coli
Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
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 manganese
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.
For E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For E. coli
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
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.
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Common questions
Is there arsenic in well water in Orange County?
Arsenic was detected in 21% of 33 public well samples in Orange 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 high is radon in well water in Orange County?
The median radon level across 53 public samples in Orange County was 400 pCi/L, with a high of 4,460 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Orange 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 Orange 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 North Carolina dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 885 samples in Orange 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.
- NCWELL private well summaries: summaries for 8 contaminants in Orange County, up to 7,286 wells each. County summaries of private well tests run by the NC State Laboratory of Public Health, 1998 to 2019, compiled by the UNC Superfund Research Program (NCWELL database). Counts are tests, not distinct wells; since 2008 every new well is tested once, so most tests are unique wells. Shares are against the NC 2L groundwater standard where one exists (manganese 50 ug/L, lead 15, iron 300) and otherwise the EPA limit. Medians are not used because more than half of results sit at the reporting limit for most analytes. Retrieved September 9, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 37,751 people on private wells in Orange 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.
- NC DEQ regulated sites: 743 regulated sites located in Orange County. Underground storage tank incidents from the North Carolina Department of Environmental Quality UST Section. Retrieved September 9, 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.