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Nitrate in Pennsylvania well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2000 to 2023Updated November 8, 2026

Nitrate is widespread, over the limit in 15% or more of tested wells, in 4 of the 28 Pennsylvania counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.

Find a nitrate test See every county

How Pennsylvania compares with the rest of the country

Across Pennsylvania, about 1 in 12 tested wells had nitrate over the EPA limit of 10 mg/L (108 of 1,329). Across all tested wells in the US it's about 1 in 12. Pennsylvania is about average, so the county you live in tells you more than the state does.

Why it matters: It's dangerous for babies under 6 months, because it keeps their blood from carrying enough oxygen.

Nitrate soaks down into groundwater from fertilizer, manure and septic systems.

Nitrate in tested wells, county by county

Share of each county's tested wells with at least one result over the EPA limit of 10 mg/L. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.

CountyWells testedWells over the limitLevel
Lancaster County 90
50%* 45 of 90
 Widespread
Blair County 20
40% 8 of 20
 Widespread
Northampton County 11
27% 3 of 11
 Widespread
Northumberland County 26
27% 7 of 26
 Widespread
Cumberland County 20
15% 3 of 20
 Widespread
Chester County 168
14% 23 of 168
 Worth checking
York County 17
12% 2 of 17
 Worth checking
Lebanon County 19
11% 2 of 19
 Worth checking
Clinton County 60
7% 4 of 60
 Worth checking
Montgomery County 31
6% 2 of 31
 Worth checking
Berks County 48
6% 3 of 48
 Worth checking
Franklin County 24
4% 1 of 24
 Rare
Lycoming County 87
1% 1 of 87
 Rare
Wayne County 128
0% 0 of 128
 Rare
Pike County 95
0% 0 of 95
 Rare
Bradford County 88
0% 0 of 88
 Rare
Potter County 48
0% 0 of 48
 Rare
Dauphin County 37
0% 0 of 37
 Rare
Bucks County 33
0% 0 of 33
 Rare
Adams County 24
0% 0 of 24
 Rare
Sullivan County 24
0% 0 of 24
 Rare
Susquehanna County 24
0% 0 of 24
 Rare
Somerset County 22
0% 0 of 22
 Rare
Erie County 17
0% 0 of 17
 Rare
Centre County 13
0% 0 of 13
 Rare
Union County 11
0% 0 of 11
 Rare
Wyoming County 11
0% 0 of 11
 Rare
Tioga County 10
0% 0 of 10
 Rare

* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:

  • Lancaster County: All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.

32 more Pennsylvania counties have 1 to 9 tested wells for nitrate, too few to rate.

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Where to get your well tested for nitrate in Pennsylvania

1

Your county health department

Pennsylvania doesn't run a statewide free testing program that we know of. Some county health departments test wells or sell kits, so call yours first.

Pennsylvania's private well page
3

A mail-in kit

Fill the bottles at your kitchen tap and mail them back. We mark the kits that include nitrate.

Compare kits

Keep reading about wells in Pennsylvania

Questions people ask about nitrate in Pennsylvania

Is there nitrate in Pennsylvania well water?

Nitrate is widespread, over the limit in 15% or more of tested wells, in 4 of the 28 Pennsylvania counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. Across Pennsylvania, about 1 in 12 tested wells had nitrate over the EPA limit of 10 mg/L (108 of 1,329). Across all tested wells in the US it's about 1 in 12. Pennsylvania is about average, so the county you live in tells you more than the state does.

Where can I get my well tested for nitrate in Pennsylvania?

Use a lab certified by Pennsylvania for drinking water, or a mail-in kit that includes nitrate from a certified lab. Some county health departments test wells too, so call yours first.

See Pennsylvania's list of certified labs (a PDF list), or compare mail-in kits.

Where these numbers come from

  • Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over the EPA limit of 10 mg/L. Wells tested for studies and monitoring, not a random sample of homes.
  • Likely overstated: our own check of who tested the wells, when and where. How we check.
  • State programs and links: Department of Environmental Protection.