Well water in Baltimore County, Maryland
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Testing recommended
tested well samples in Baltimore County exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
The strongest signal is copper: 14% of 29 local samples were above the limit, too few samples to carry the headline but first on the test list below.
513 test results across 12 contaminants from at least 90 wells, 1943 to 2003; chloride has the most at 111. Data refreshed September 3, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
What individual samples found
Each row summarizes every public sample for that contaminant inside Baltimore 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 |
|---|---|---|---|---|---|---|
| Copper 1944 to 2003 | 29 | 93% | 0.03 | 4.2 | 1.3 mg/L EPA limit | |
| Nitrate 1943 to 2003 | 100 | 82% | 0.435 | 9,740 | 10 mg/L EPA limit | |
| Lead 1981 to 2003 | 25 | 88% | 0 | 500 | 15 ug/L EPA limit | |
| Fluoride 1943 to 2003 | 65 | 51% | 0.1 | 180 | 4 mg/L EPA limit | |
| Arsenic 1981 to 2003 | 25 | 100% | 1 | 2 | 10 ug/L EPA limit | |
| Chloride 1943 to 2003 | no limit | 111 | 100% | 81 | 6,000 | 250 mg/L nuisance level |
| Iron 1943 to 2003 | no limit | 86 | 99% | 940 | 106,000 | 300 ug/L nuisance level |
| Sodium 1944 to 2003 | no limit | 38 | 100% | 48.5 | 3,000 | 20 mg/L health guideline |
| Manganese 1954 to 2003 | no limit | 30 | 100% | 689 | 100,000 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (2), Uranium (1), Radon (1).
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 copper (14% of 29 samples), nitrate (9% of 100 samples), and lead (8% of 25 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 Baltimore County
- 1Copper14% of 29 local samples were above the limit.
- 2Nitrate9% of 100 local samples were above the limit.
- 3Lead8% of 25 local samples were above the limit.
- 4Fluoride2% of 65 local samples were above the limit.
- 5Coliform bacteriaRecommended for every private well, every year.
- 6RadonMedian local reading is 170 pCi/L.
- 7ChlorideDetected in 100% of local samples.
- 8Volatile organic compounds (VOCs)2 hazardous waste sites on record locally.
- 9Metals panel2 hazardous waste sites on record locally.
Test your Baltimore County well for copper, 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 Maryland: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Baltimore County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Baltimore 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 Baltimore County
MDE Land Restoration Program sites records 2 hazardous waste sites in Baltimore County, among 582 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.
- 2
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 580
- other remediation projects
Treatment that fits the local profile
Copper
Neutralizing filter to raise pH; Point-of-use reverse osmosis
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
Chloride
Point-of-use reverse osmosis; 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 copper
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For copper
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
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 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 Baltimore County
No water treatment company serves Baltimore 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 Baltimore County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Baltimore County?
Arsenic was detected in 100% of 25 public well samples in Baltimore 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 Baltimore 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 Baltimore 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: 513 samples in Baltimore 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.
- MDE Land Restoration Program sites: 582 regulated sites located in Baltimore 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.