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Ohio water hardness, by utility.

52 Ohio utilities serving 3.9 million people as they report it, from the state’s own results. Hardness is the calcium and magnesium in water; EPA sets no limit for it.

The short answer

5 utilities serving 1.4 million people have water in more than one band. Among those in one band, moderately hard water reaches the most people: 7 utilities serving 1.3 million.

The largest, Columbus Public Water System, is moderately hard to hard depending on the source, 98 to 125 mg/L (5.7 to 7.3 grains per gallon).

Very hard

Above 180 mg/L (10.5 grains per gallon). 26 utilities serving 241,670 people; the 25 largest are here.

Ohio utilities: very hard water
UtilityBased inServesHardness, mg/LGrains per gallon
Aqua Ohio - Massillon PWSMassillon95,63636321.2
Aqua Ohio - MarionMarion47,10277845.5
Wooster City PWSWooster26,61831518.4
Licking Regional Water DistrictBaltimore17,81835921
Jackson Co. Water Company - WTPJackson15,98429817.4
Rattlesnake PWSWashington Court House7,68546126.9
Warren Comm W and S Assn 2Marietta7,21532419
Gallipolis PWSGallipolis7,13425114.7
Covington Village PWSCovington2,71819011.1
Versailles Village PWSVersailles2,68751630.2
St Henry VillageSt Henry2,59683348.7
Columbus Grove VillageColumbus Grove2,13751229.9
Winesburg Area Development CorporationWinesburg1,57522012.9
Aqua Ohio - la Rue Village PWSMarion80051830.3
Oakwood Village PWSOakwood72737321.8
Malta Village PWSMalta67128216.5
Mount Eaton Village PWSWinesburg42530617.9
Hudson Estates PWSMorgantown41025214.7
Chickasaw VillageChickasaw35866638.9
Towbridge DevelopmentHudson35233819.8
Mantua Mobile Home ParkDurham25025314.8
Martinsburg Village PWSMartinsburg24024914.6
Aqua Ohio - Mansfield System #08Massillon17026415.4
Carvel Manor MHPDurham14847427.7
Granger Lake Condo 4 PWSMedina10824814.5
All 26 with very hard water

Hard

121 to 180 mg/L (7.1 to 10.5 grains per gallon). 8 utilities serving 1 million people, largest first.

Ohio utilities: hard water
UtilityBased inServesHardness, mg/LGrains per gallon
Cincinnati Public Water SystemCincinnati800,000126 to 1407.4 to 8.2
Dayton Public Water SystemDayton141,407131 to 1507.7 to 8.7
Findlay City PWSFindlay54,0401508.8
Coldwater VillageColdwater4,7741277.4
Carrollton VillageCarrollton3,0551518.8
Cardington Village PWSCardington2,0791207
Northwestern W and SD - McCombBowling Green1,5271287.5
Nashville Village PWSBig Prairie19717310.1

Moderately hard

61 to 120 mg/L (3.6 to 7 grains per gallon). 7 utilities serving 1.3 million people, largest first.

Ohio utilities: moderately hard water
UtilityBased inServesHardness, mg/LGrains per gallon
Cleveland Public Water SystemCleveland1,308,9551176.8
Waterville CityWaterville6,5001056.1
Northwestern W and SD - WestonBowling Green3,6481066.2
Genoa VillageGenoa3,110824.8
New Knoxville VillageNew Knoxville946854.9
Waterford Water/Sewer AssociationWaterford770865
Little Chippewa EstatesMorgantown153885.1

Soft

Up to 60 mg/L (3.5 grains per gallon). 6 utilities serving 7,636 people, largest first.

Ohio utilities: soft water
UtilityBased inServesHardness, mg/LGrains per gallon
Doylestown Village PWSDoylestown3,0510.10
New Bremen VillageNew Bremen3,0344.40.3
Tuscarawas VillageTuscarawas1,0560.40
Deer Meadows MHPMorgantown24240.2
Hayden Heights MHPMorgantown188563.2
Country Meadows Condo.Piqua6550.3

Varies

Water in more than one band, depending on where or when it was sampled: each is given as its range, softest to hardest, and its report says more. 5 utilities serving 1.4 million people, largest first.

Ohio utilities: varies water
UtilityBased inServesHardness, mg/LGrains per gallon
Columbus Public Water SystemColumbus1,309,46898 to 1255.7 to 7.3
Kent City PWSKent29,662145 to 1828.5 to 10.6
Jefferson Water and Sewer District PWSBlacklick11,294128 to 5357.5 to 31.3
Wright State UniversityDayton8,948143 to 4298.4 to 25.1
Bloomfield Water CompanyMillersburg95088 to 2515.1 to 14.7

Source: Ohio Environmental Protection Agency, Division of Drinking and Ground Waters, 48 utilities, results from Jan. 6, 2020 to Dec. 31, 2025, read Oct. 17, 2026. Each sampling point is taken at its median; a figure is typical where every point falls in one band.

Also: 4 utilities’ own water quality reports, read by hand, each named on the utility’s page.

Bands are the U.S. Geological Survey’s, at 17.1 mg/L to the grain. People served is what each utility reports; where one sells water to another, the same people can be counted twice. How hardness is measured here.

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