Pennsylvania well water by county
What Penn State's well tests show across the state, and how your county compares.
Statewide
From 24,726 drinking water samples tested by the Penn State Agricultural Analytical Services Lab, 2007 to 2025. Owners who test often have a problem, so rates may run higher than for all wells.
Western Pennsylvania
Armstrong County
70% of well samples failed for bacteria. 126 samples tested.
See local results →Beaver County
52% of well samples failed for bacteria. 220 samples tested.
See local results →Erie County
52% of well samples failed for bacteria. 154 samples tested.
See local results →Mercer County
43% of well samples failed for bacteria. 299 samples tested.
See local results →North Central Pennsylvania
Lycoming County
44% of well samples failed for bacteria. 297 samples tested.
See local results →Tioga County
49% of well samples failed for bacteria. 216 samples tested.
See local results →Central Pennsylvania
Centre County
43% of well samples failed for bacteria. 3,046 samples tested.
See local results →Columbia County
45% of well samples failed for bacteria. 813 samples tested.
See local results →Northumberland County
46% of well samples failed for bacteria. 196 samples tested.
See local results →Schuylkill County
52% of well samples failed for bacteria. 149 samples tested.
See local results →Union County
39% of well samples failed for bacteria. 333 samples tested.
See local results →Northeast Pennsylvania
Carbon County
29% of well samples failed for bacteria. 184 samples tested.
See local results →Luzerne County
38% of well samples failed for bacteria. 618 samples tested.
See local results →Pike County
25% of well samples failed for bacteria. 556 samples tested.
See local results →Wayne County
28% of well samples failed for bacteria. 712 samples tested.
See local results →South Central Pennsylvania
Adams County
49% of well samples failed for bacteria. 225 samples tested.
See local results →Dauphin County
40% of well samples failed for bacteria. 353 samples tested.
See local results →Lebanon County
36% of well samples failed for bacteria. 150 samples tested.
See local results →Southeast Pennsylvania
Berks County
40% of well samples failed for bacteria. 464 samples tested.
See local results →Bucks County
32% of well samples failed for bacteria. 614 samples tested.
See local results →Chester County
29% of well samples failed for bacteria. 490 samples tested.
See local results →Lancaster County
42% of well samples failed for bacteria. 555 samples tested.
See local results →Lehigh County
34% of well samples failed for bacteria. 378 samples tested.
See local results →Don't see your county?
Penn State publishes results for every county. Here are the rest: Allegheny, Bedford, Blair, Bradford, Butler, Cambria, Cameron, Clarion, Clearfield, Clinton, Crawford, Cumberland, Delaware, Elk, Fayette, Forest, Franklin, Fulton, Greene, Huntingdon, Indiana, Jefferson, Juniata, Lackawanna, Lawrence, McKean, Mifflin, Monroe, Montgomery, Montour, Northampton, Perry, Philadelphia, Potter, Snyder, Somerset, Sullivan, Susquehanna, Venango, Warren, Washington, Westmoreland, Wyoming, York.
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