Wisconsin utilities with very hard water.

Above 180 mg/L (10.5 grains per gallon). 580 utilities serving 1.6 million people as they report it, largest first.

1 to 100 of 580, by people served

Wisconsin utilities with very hard water, 1 to 100
Utility	Based in	Serves	Hardness, mg/L	Grains per gallon
Madison Water Utility	Madison	272,000	345	20.2
Waukesha Water Utility	Waukesha	70,718	320	18.7
Janesville Water Utility	Janesville	64,415	363	21.2
Fond Du Lac Waterworks	Fond Du Lac	44,678	375	21.9
Sun Prairie Utilities	Sun Prairie	39,300	330	19.3
City of Beloit	Beloit	36,677	337	19.7
West Bend Waterworks	West Bend	32,149	408	23.8
Fitchburg Utility Dist 1	Fitchburg	29,900	270	15.8
Brookfield Water Utility	Brookfield	29,070	390	22.8
Watertown Waterworks	Watertown	23,945	355	20.8
Middleton Waterworks	Middleton	23,868	325	19
Germantown Water Utility	Germantown	20,027	420	24.6
Marshfield Utilities	Marshfield	18,815	268	15.6
Onalaska Waterworks	Onalaska	18,000	344	20.1
Kaukauna Utilities	Kaukauna	17,493	655	38.3
Hartford Waterworks	Hartford	15,805	425	24.9
Oconomowoc Waterworks	Oconomowoc	15,805	320	18.7
Waunakee Waterworks	Waunakee	14,879	280	16.4
Verona Waterworks	Verona	14,030	362	21.2
Whitewater Waterworks	Whitewater	14,000	320	18.7
Plover Waterworks	Plover	13,486	250	14.6
Stoughton Waterworks	Stoughton	13,078	325	19
Cedarburg L & W Commission	Cedarburg	12,500	388	22.7
Fort Atkinson Waterworks	Fort Atkinson	12,390	278	16.2
Grafton Waterworks	Grafton	12,269	360	21.1
Platteville Waterworks	Platteville	12,268	317	18.5
Sussex Village Hall & Water Utility	Sussex	11,750	315	18.4
Greenville Utilities Vil of	Greenville	11,340	290	17
Oregon Waterworks	Oregon	11,200	310	18.1
Monroe Waterworks	Monroe	10,780	285	16.7
Deforest Waterworks	Deforest	10,500	265	15.5
Holmen Waterworks	Holmen	10,147	296	17.3
Sturgeon Bay Waterworks	Sturgeon Bay	9,700	340	19.9
McFarland Waterworks	Mc Farland	9,676	394	23
Shawano Waterworks	Shawano	9,610	350	20.5
Cottage Grove Waterworks	Cottage Grove	9,345	348	20.4
Hartland Waterworks	Hartland	9,212	440	25.7
Delavan Waterworks	Delavan	9,028	395	23.1
Plymouth Utilities	Plymouth	8,964	394	23
Pewaukee City Water and Sewer Utility	Pewaukee	8,671	303	17.7
Monona Waterworks	Monona	8,624	467	27.3
Jackson Waterworks	Jackson	8,397	340	19.9
Mukwonago Waterworks	Mukwonago	8,190	375	21.9
Pewaukee Village Waterworks	Pewaukee	8,166	285	16.7
Jefferson Waterworks	Jefferson	7,926	273	15.9
MT Horeb Waterworks	Mount Horeb	7,756	361	21.1
Ripon Water Utility	Ripon	7,716	370	21.6
Lake Geneva Utility Commission	Lake Geneva	7,107	375	21.9
Town of Brookfield San Dist 4	Brookfield	6,419	535	31.3
Lake Mills Waterworks	Lake Mills	6,211	330	19.3
Prairie Du Chien Waterworks	Prairie Du Chien	6,005	312	18.2
Evansville Waterworks	Evansville	5,703	314	18.4
Slinger Water Utility	Slinger	5,659	485	28.4
Milton Waterworks	Milton	5,588	353	20.6
Edgerton Waterworks	Edgerton	5,512	323	18.9
North Fond Du Lac Waterworks	North Fond Du Lac	5,414	325	19
Waterford Waterworks	Waterford	5,368	357	20.9
Mayville Waterworks	Mayville	5,112	300	17.5
Richland Center Waterworks	Richland Center	5,100	215	12.6
East Troy Waterworks	East Troy	5,054	348	20.3
West Salem Waterworks	West Salem	5,045	245	14.3
Clintonville Utilities	Clintonville	4,635	310	18.1
Windsor Water Utility South	Windsor	4,607	260	15.2
Sheboygan TN Waterworks	Sheboygan	4,596	391	22.8
Dodgeville Waterworks	Dodgeville	4,583	315	18.4
Kewaskum Waterworks	Kewaskum	4,309	470	27.5
Saukville Waterworks	Saukville	4,268	365	21.3
Cross Plains Waterworks	Cross Plains	4,100	370	21.6
Pulaski Waterworks	Pulaski	4,040	283	16.5
Prairie Du Sac Waterworks	Prairie Du Sac	4,006	266	15.5
Algoma TN Sanitary Dist 1	Oshkosh	3,935	310	18.1
Kiel Waterworks	Kiel	3,932	420	24.6
Lancaster Waterworks	Lancaster	3,907	295	17.3
Marshall Waterworks	Marshall	3,862	300	17.5
Waupun Correctional Inst	Waupun	3,706	250	14.6
Horicon Waterworks	Horicon	3,682	236	13.8
Omro Waterworks	Omro	3,629	350	20.5
Seymour Waterworks	Seymour	3,601	285	16.7
Waterloo Waterworks	Waterloo	3,520	425	24.9
Sauk City Waterworks	Sauk City	3,518	285	16.7
Somerset Waterworks	Somerset	3,334	196	11.4
Johnson Creek Waterworks	Johnson Creek	3,318	270	15.8
Ellsworth Waterworks	Ellsworth	3,304	330	19.3
Boscobel Waterworks	Boscobel	3,237	275	16.1
Brodhead Waterworks	Brodhead	3,216	294	17.2
Lodi Waterworks	Lodi	3,146	308	18
Oostburg Waterworks	Oostburg	3,110	388	22.7
Lake Como Sanitary Dist 1	Lake Geneva	3,038	285	16.7
Hortonville Water Utility	Hortonville	3,028	362	21.2
New Holstein Waterworks	New Holstein	3,012	371	21.7
Oconto Falls Waterworks	Oconto Falls	2,892	225	13.2
Kewaunee Waterworks	Kewaunee	2,848	407	23.8
Mendota Mental Health Inst	Madison	2,787	415	24.3
Rome Water Utility	Nekoosa	2,775	182	10.6
Genoa City Waterworks	Genoa City	2,766	434	25.4
Luxemburg Waterworks	Luxemburg	2,737	390	22.8
Belleville Waterworks	Belleville	2,712	295	17.3
Lomira Waterworks	Lomira	2,701	418	24.4
Denmark Waterworks	Denmark	2,684	405	23.7
Juneau Waterworks	Juneau	2,627	285	16.7

Source: Wisconsin Department of Natural Resources, Drinking Water Program, 940 utilities, results from Feb. 4, 2015 to Sept. 24, 2026, read Oct. 10, 2026. Each sampling point is taken at its median; a figure is typical where every point falls in one band.

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.

1 to 100 of 580, by people served

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