privatewelldata / States / North Carolina / Nitrate
Nitrate in well water in North Carolina
5% of 1,964 sampled wells in North Carolina had nitrate above the EPA limit of 10 mg/L (as nitrogen) (latest result per well, 57 counties, samples 1932–2023). The highest county share was Wake County: 29% of 49 wells. Data updated 2026-10-18.
of sampled wells above 10 mg/L (as nitrogen)
wells with a result
counties with data
counties where 1 in 4+ wells were above
Nitrate in wells most often comes from fertilizer, manure and septic systems, so shallow wells near fields or septic fields are more exposed, and levels can change with the seasons. Only a lab test shows it. Federal limits apply to public water systems; a private well is the owner's responsibility to test (EPA).
% of sampled wells above the EPA limit (latest result per well; counties with 10+ wells). Source: USGS/EPA Water Quality Portal, 2026-10-18 · privatewelldata.com
Nitrate by county in North Carolina
| County | Above 10 mg/L (as nitrogen) | Median | 90th pct. | Years |
|---|---|---|---|---|
| Wake County | 29% of 49 | 1.28 mg/L as N | 87.5 | 1961–2007 |
| Sampson County | 26% of 69 | 0.07 mg/L as N | 29 | 1948–2022 |
| Greene County | 23% of 87 | 0.14 mg/L as N | 22 | 1947–2014 |
| Anson County | 19% of 21 | 1.514 mg/L as N | 14.006 | 1947–1964 |
| Duplin County | 19% of 32 | 0.06 mg/L as N | 13.6 | 1947–2014 |
| Edgecombe County | 17% of 29 | 0 mg/L as N | 12 | 1942–2022 |
| Columbus County | 10% of 20 | 0.113 mg/L as N | 0.361 | 1948–1998 |
| Onslow County | 9% of 46 | 0.019 mg/L as N | 0.791 | 1941–2021 |
| Granville County | 7% of 14 | 0.963 mg/L as N | 7.91 | 1961–2014 |
| Moore County | 7% of 14 | 0.07 mg/L as N | 3.01 | 1948–2012 |
| Northampton County | 7% of 14 | 0.023 mg/L as N | 0.361 | 1942–1965 |
| Johnston County | 7% of 74 | 0.15 mg/L as N | 6 | 1947–1999 |
| Warren County | 6% of 18 | 0.316 mg/L as N | 2.26 | 1962–2014 |
| Orange County | 4% of 70 | 0.285 mg/L as N | 2.29 | 1950–2013 |
| Bladen County | 4% of 24 | 0.023 mg/L as N | 0.181 | 1947–2022 |
| Chowan County | 4% of 49 | 0.05 mg/L as N | 5.9 | 1942–1995 |
| Hertford County | 4% of 27 | 0.07 mg/L as N | 6.303 | 1948–2022 |
| Pitt County | 3% of 74 | 0.08 mg/L as N | 6 | 1942–2022 |
| Dare County | 3% of 37 | 0.05 mg/L as N | 0.25 | 1947–1995 |
| Lee County | 3% of 38 | 0.254 mg/L as N | 2.417 | 1954–2012 |
| Beaufort County | 2% of 46 | 0.034 mg/L as N | 0.361 | 1942–2022 |
| Wayne County | 1% of 87 | 0.05 mg/L as N | 4.9 | 1942–2014 |
| New Hanover County | 0% of 123 | 0.04 mg/L as N | 0.331 | 1941–2022 |
| Craven County | 0% of 109 | 0.012 mg/L as N | 0.09 | 1941–2022 |
| Brunswick County | 0% of 93 | 0 mg/L as N | 0.239 | 1948–2017 |
| Mecklenburg County | 0% of 92 | 0.06 mg/L as N | 0.9 | 1983–1994 |
| Guilford County | 0% of 72 | 0.21 mg/L as N | 1.6 | 1985–2007 |
| Pasquotank County | 0% of 35 | 0.023 mg/L as N | 0.542 | 1932–2017 |
| Martin County | 0% of 27 | 0.09 mg/L as N | 0.41 | 1947–2022 |
| Iredell County | 0% of 26 | 0.135 mg/L as N | 1.41 | 2002–2014 |
| Lenoir County | 0% of 26 | 0.05 mg/L as N | 0.14 | 1943–2021 |
| Perquimans County | 0% of 24 | 0.08 mg/L as N | 0.95 | 1958–2023 |
| Washington County | 0% of 24 | 0.07 mg/L as N | 1.1 | 1943–2022 |
| Pender County | 0% of 23 | 0 mg/L as N | 0.07 | 1941–2022 |
| Pamlico County | 0% of 22 | 0 mg/L as N | 0.05 | 1943–2022 |
| Rockingham County | 0% of 21 | 0.07 mg/L as N | 8.75 | 1955–2007 |
| Robeson County | 0% of 20 | 0.05 mg/L as N | 0.07 | 1945–1981 |
| Lincoln County | 0% of 18 | 1.2 mg/L as N | 5.105 | 1991–1992 |
| Wilson County | 0% of 18 | 0.05 mg/L as N | 0.8 | 1942–2021 |
| Buncombe County | 0% of 17 | 0 mg/L as N | 0.05 | 2003–2014 |
| Carteret County | 0% of 17 | 0 mg/L as N | 0.113 | 1941–2014 |
| Halifax County | 0% of 17 | 0.25 mg/L as N | 3.614 | 1941–1966 |
| Hyde County | 0% of 17 | 0.14 mg/L as N | 0.203 | 1959–2014 |
| Durham County | 0% of 16 | 0.055 mg/L as N | 0.542 | 1963–2018 |
| Harnett County | 0% of 16 | 0.023 mg/L as N | 0.294 | 1947–2010 |
| Montgomery County | 0% of 16 | 0.23 mg/L as N | 1.003 | 1948–2007 |
| Currituck County | 0% of 15 | 0.59 mg/L as N | 4.1 | 1961–2023 |
| Bertie County | 0% of 14 | 0.186 mg/L as N | 0.361 | 1942–2022 |
| Franklin County | 0% of 14 | 0.283 mg/L as N | 1.04 | 1948–2007 |
| Randolph County | 0% of 14 | 0.01 mg/L as N | 0.124 | 2007–2014 |
| Nash County | 0% of 13 | 0.023 mg/L as N | 0.542 | 1941–2014 |
| Camden County | 0% of 12 | 0.05 mg/L as N | 0.294 | 1962–2017 |
| Person County | 0% of 12 | 0.52 mg/L as N | 2.94 | 1962–2007 |
| Tyrrell County | 0% of 12 | 0.017 mg/L as N | 0.018 | 1962–2005 |
| Chatham County | 0% of 10 | 0.07 mg/L as N | 0.168 | 2007–2014 |
| Cumberland County | 0% of 10 | 0.046 mg/L as N | 2.711 | 1951–1959 |
| Hoke County | 0% of 10 | 0.531 mg/L as N | 1.1 | 1951–1963 |
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Download this table (CSV) · public-domain source data: Water Quality Portal (USGS, EPA, NWQMC). How we calculate these numbers.
How North Carolina compares
Share of sampled wells above the EPA nitrate limit in each state we cover (states with 100+ wells).
| # | State | Above 10 mg/L (as nitrogen) |
|---|---|---|
| 1 | California | 10% of 16,344 |
| 2 | Pennsylvania | 8% of 6,478 |
| 3 | Minnesota | 6% of 7,259 |
| 4 | North Carolina | 5% of 1,964 |
| 5 | New York | 5% of 6,236 |
| 6 | Massachusetts | 4% of 2,556 |
| 7 | New Jersey | 4% of 3,915 |
| 8 | Wisconsin | 4% of 3,666 |
| 9 | Virginia | 3% of 1,394 |
| 10 | Maine | 2% of 726 |
| 11 | Michigan | 2% of 1,970 |
| 12 | Ohio | 1% of 1,239 |
| 13 | New Hampshire | 0% of 1,685 |
Where to test: official lab list for North Carolina
About this data
- Each well counts once, using its latest nitrate result in the Water Quality Portal (siteType = Well), downloaded 2026-10-18.
- Results reported as "not detected" count as below the limit. Results far outside the plausible range are withheld for review, not shown.
- Sampled wells include monitoring and research wells, not only household wells, and are not a random sample, so the share is a guide to local risk, not a rate for all homes.
- The limit is the EPA maximum contaminant level for public water systems (EPA).
Questions
Is nitrate common in North Carolina well water?
In our data, 95 of 1,964 sampled wells in North Carolina (5%) had a latest nitrate result above the EPA limit of 10 mg/L (as nitrogen), across 57 counties. That ranks North Carolina 4 of 13 states we cover for this share.
Which North Carolina counties have the most wells above the nitrate limit?
Among counties with at least 10 sampled wells: Wake County (29%, 14 of 49 wells); Sampson County (26%, 18 of 69 wells); Greene County (23%, 20 of 87 wells).
Does this tell me whether my well is safe?
No. These are past results from wells sampled by USGS, EPA and state programs, including monitoring wells, and levels differ from well to well. The only way to know your water is to test your own well at a certified lab.
How do I test my well for nitrate in North Carolina?
Order a nitrate test from a lab on North Carolina's official certified-lab list (linked on this page) and ask for its bottles and sampling instructions. Our test helper suggests what else to test for at the same time.
What should I do if my nitrate result is above 10 mg/L (as nitrogen)?
Retest to confirm, use another water source for drinking and cooking while you sort it out, and look at certified treatment options. Our guide walks through each step with sources.