countyscore

Best Water Quality Counties in Ohio

EPA drinking water health violations and safety grades Compare rankings across all 88 counties.

Average Water Quality Score
56/100
Top County
Butler County
Counties Ranked
88

Top 10

#1
Butler County
OH
86/100
#2
Cuyahoga County
OH
86/100
#3
Delaware County
OH
86/100
#4
Erie County
OH
86/100
#5
Gallia County
OH
86/100
#6
Highland County
OH
86/100
#7
Knox County
OH
86/100
#8
Marion County
OH
86/100
#9
Mercer County
OH
86/100
#10
Morrow County
OH
86/100

All Ohio Counties Ranked

#CountyWater Quality ScoreOverall Score
1Butler County, OH
86
36.2
2Cuyahoga County, OH
86
30.4
3Delaware County, OH
86
38.6
4Erie County, OH
86
47.4
5Gallia County, OH
86
48
6Highland County, OH
86
53.4
7Knox County, OH
86
53.7
8Marion County, OH
86
36.5
9Mercer County, OH
86
65.5
10Morrow County, OH
86
51.7
11Pike County, OH
86
50.9
12Scioto County, OH
86
43.7
13Wyandot County, OH
86
67.1
14Hamilton County, OH
71.8
30.8
15Mahoning County, OH
71.1
38.6
16Greene County, OH
70.8
37.9
17Lake County, OH
70.1
49.4
18Lucas County, OH
70.1
24.8
19Montgomery County, OH
69.8
29.3
20Clermont County, OH
69.7
45.9
21Franklin County, OH
68.8
41.9
22Summit County, OH
68.6
33.7
23Medina County, OH
68.2
53.9
24Fairfield County, OH
67.7
39.9
25Miami County, OH
67.3
45.8
26Ashtabula County, OH
66.8
46.5
27Licking County, OH
66.5
37.9
28Ross County, OH
66.2
38
29Tuscarawas County, OH
65.6
47.3
30Sandusky County, OH
65.3
55.5
31Columbiana County, OH
65.1
53.1
32Union County, OH
65
49.6
33Warren County, OH
64.5
47.3
34Ashland County, OH
64.4
52.8
35Wood County, OH
63.2
51.1
36Clinton County, OH
62.8
46.8
37Lawrence County, OH
62.6
53.2
38Lorain County, OH
62.6
41.7
39Washington County, OH
62.6
49.9
40Portage County, OH
62.3
42.8
41Stark County, OH
62
38
42Champaign County, OH
61.5
49.2
43Jackson County, OH
61.4
49.8
44Allen County, OH
60.8
34
45Huron County, OH
60.6
56.9
46Adams County, OH
60.1
55.6
47Auglaize County, OH
59.8
58.4
48Coshocton County, OH
59.4
52.8
49Shelby County, OH
59.3
47.9
50Fayette County, OH
57.7
40.4
51Belmont County, OH
55.7
58.5
52Trumbull County, OH
54.8
39.3
53Wayne County, OH
52.2
45
54Meigs County, OH
51.8
51.3
55Preble County, OH
51.6
57.4
56Brown County, OH
51
58.4
57Seneca County, OH
50.6
54.2
58Darke County, OH
50.4
62.4
59Pickaway County, OH
49.7
41.7
60Noble County, OH
49.3
70.4
61Williams County, OH
48.5
58.5
62Madison County, OH
46.2
47.8
63Ottawa County, OH
45.7
59.6
64Jefferson County, OH
44.4
47.8
65Vinton County, OH
43
48.2
66Logan County, OH
42.9
56
67Guernsey County, OH
42.6
52.2
68Richland County, OH
42.4
37.8
69Carroll County, OH
42
56.7
70Clark County, OH
41.6
32.3
71Hardin County, OH
39.9
50.9
72Hocking County, OH
39.5
39.3
73Athens County, OH
39
41.4
74Geauga County, OH
35.7
55.7
75Hancock County, OH
34.4
46.4
76Monroe County, OH
32.5
64.8
77Crawford County, OH
31.9
48.5
78Holmes County, OH
30.8
56.3
79Muskingum County, OH
29.3
42.1
80Harrison County, OH
24.5
54.6
81Perry County, OH
23.9
59.4
82Putnam County, OH
23.7
65.2
83Morgan County, OH
23.6
52.5
84Paulding County, OH
17.9
57.1
85Van Wert County, OH
13.6
54.9
86Defiance County, OH
12.1
55.5
87Fulton County, OH
11.8
49.8
88Henry County, OH
5.9
53.4

Data Source

Water Quality data from WaterByCounty. See full details at WaterByCounty. Data updated February 2026.