Well water in Caroline County, Maryland
1in4
Testing strongly recommended
tested well samples in Caroline County exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
1,327 test results across 15 contaminants from at least 122 wells, 1953 to 2024; nitrate has the most at 359. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 20,137 people in Caroline County get their drinking water from a private well, per USGS 2015 county water use. That is about 62% of residents.
Separately, the USGS national arsenic model estimates that 10% of the 20,137 people on private wells in Caroline County draw water above 10 ug/L (the model's range is 7% to 15%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Caroline 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 1953 to 2024 | 359 | 81% | 5.2 | 106 | 10 mg/L EPA limit | |
| Lead 1984 to 2024 | 68 | 76% | 0.018 | 20 | 15 ug/L EPA limit | |
| Fluoride 1953 to 2024 | 78 | 56% | 0.1 | 4.4 | 4 mg/L EPA limit | |
| Copper 1953 to 2024 | 70 | 46% | 0 | 0.05 | 1.3 mg/L EPA limit | |
| Arsenic 1988 to 2024 | 52 | 50% | 0.01 | 7 | 10 ug/L EPA limit | |
| Uranium 2001 to 2024 | 35 | 71% | 0.01 | 0.223 | 30 ug/L EPA limit | |
| Radium (226 + 228) 2012 to 2013 | 21 | 52% | 0.07 | 0.88 | 5 pCi/L EPA limit | |
| Chloride 1953 to 2024 | no limit | 180 | 100% | 8.13 | 377 | 250 mg/L nuisance level |
| Iron 1953 to 2024 | no limit | 170 | 89% | 35.8 | 27,000 | 300 ug/L nuisance level |
| Sodium 1953 to 2024 | no limit | 151 | 100% | 6.1 | 278 | 20 mg/L health guideline |
| Manganese 1953 to 2024 | no limit | 100 | 85% | 30 | 250 | 300 ug/L health guideline |
| Radon 1988 to 2012 | no limit | 35 | 97% | 280 | 1,300 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (6), PFOS (1), PFOA (1).
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 | 30%273 samples | 31%32 samples | 8%40 samples | 43%14 samples |
| Fluoride | 3%40 samples | 0%11 samples | 0%20 samples | n/a |
| Lead | 3%30 samples | 0%11 samples | 0%20 samples | n/a |
| Copper | 0%35 samples | n/a | 0%20 samples | n/a |
| Arsenic | 0%13 samples | 0%12 samples | 0%20 samples | n/a |
Nitrate above the limit in Caroline County fell from 31% of 32 samples in the 2000s to 8% of 40 in the 2010s.
Fluoride, lead, copper have 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
The contaminants most often above their limit here are nitrate (28% of 359 samples), lead (1% of 68 samples), and fluoride (1% of 78 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 Caroline County
- 1Nitrate28% of 359 local samples were above the limit.
- 2Lead1% of 68 local samples were above the limit.
- 3Fluoride1% of 78 local samples were above the limit.
- 4RadonMedian local reading is 280 pCi/L.
- 5E. coliAbove the limit in 1 of 6 local samples; too few to quote a rate.
- 6ChlorideDetected in 100% of local samples.
- 7IronDetected in 89% of local samples.
Test your Caroline County well for nitrate, lead and fluoride
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 Maryland: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Caroline County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Caroline County
Northern Atlantic Coastal Plain aquifer system
Semiconsolidated sand. Coastal plain sands like these give steady yields at moderate depth. Salt water and sodium are the usual issues near the coast, and nitrate where the water table is shallow; arsenic and radon from bedrock are less common.
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 Maryland
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.
Contamination sources on record in Caroline County
MDE Land Restoration Program sites records 16 regulated sites in Caroline County, among 16 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.
- 16
- other remediation projects
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Lead
Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
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 lead
Aquasana Claryum 3-Stage under-sink filter
under-sink or countertop, about $175
Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
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
Get on the list for a free in-home water test in Caroline County
No water treatment company serves Caroline County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Caroline County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Caroline County?
Arsenic was detected in 50% of 52 public well samples in Caroline 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 Caroline County?
The median radon level across 35 public samples in Caroline County was 280 pCi/L, with a high of 1,300 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Caroline 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 Caroline 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 Maryland dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 1,327 samples in Caroline 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 20,137 people on private wells in Caroline 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.
- MDE Land Restoration Program sites: 16 regulated sites located in Caroline County. Brownfield, voluntary cleanup and Superfund sites from the Maryland Department of the Environment Land Restoration Program. Retrieved September 18, 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.