Nitrate in Maryland well water

In Maryland, 18% of 10,124 tested private well samples exceeded the EPA limit for nitrate (10 mg/L).

Nitrate reaches wells from fertilizer, septic systems and manure. Above the limit it can cause methemoglobinemia (blue baby syndrome) in infants under six months, and long-term exposure is associated with some cancers. Shallow and dug wells near farmland or dense septic systems are most at risk.

Check your nitrate number

Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.

Test your Maryland well for nitrate

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 $209 Already tested? Upload the report

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Systems that remove nitrate

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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.

Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.

Where to get a well tested for nitrate in Maryland: certified labs, state programs and prices.

By county, from individual samples

Public monitoring samples against the EPA limit (10 mg/L); counties with at least 30 samples.

County	Above EPA limit	Samples	Detected	Median	Highest
Kent	50%	723	83%	10.2	191 mg/L
Queen Anne's	40%	405	74%	7.94	260 mg/L
Washington	37%	354	94%	6.6	336 mg/L
Calvert	31%	1,370	98%	9.1	57.5 mg/L
Caroline	28%	359	81%	5.2	106 mg/L
Carroll	20%	281	99%	4.8	110 mg/L
Frederick	17%	404	95%	3.05	178 mg/L
Wicomico	13%	458	64%	0.338	166 mg/L
Montgomery	13%	253	94%	2.54	40.4 mg/L
Dorchester	13%	295	67%	0.113	71.1 mg/L
Harford	11%	491	92%	2.6	53.1 mg/L
Baltimore	9%	1,368	96%	1.69	70.8 mg/L
Baltimore	9%	100	82%	0.435	9,740 mg/L
Talbot	8%	120	68%	0.075	61.2 mg/L
Howard	7%	867	83%	1.7	57.5 mg/L

District 1, Dixon, Queen Anne's County62% of 210
District 2, Kennedyville, Kent County61% of 572
District 1, Sharpsburg, Washington County58% of 81
District 6, Hillsboro, Caroline County52% of 63
District 8, American Corner, Caroline County45% of 44
District 8, Hampstead, Carroll County41% of 66
District 1, Fork, Dorchester County35% of 48
District 6, Ruthsburg, Queen Anne's County34% of 35
District 1, Solomons Island, Calvert County33% of 1,252
District 5, Federalsburg, Caroline County32% of 31
District 5, Parsons, Wicomico County31% of 42
District 4, Baltimore County26% of 86
District 9, Montgomery County25% of 52
District 3, Denton, Caroline County21% of 100
District 3, Worton (Betterton), Kent County20% of 30
District 4, Pittsburg, Wicomico County19% of 54
District 4, Chapel, Talbot County18% of 55
District 7, Baltimore County18% of 84
District 2, Anne Arundel County18% of 34
District 5, Baltimore County17% of 101

Sources

Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. nitrate counts and shares are listed on each county and town page with their sources.

Analysis: Nitrate in private wells, decade by decade, from the same public records.