Illinois utilities with hard water.

121 to 180 mg/L (7.1 to 10.5 grains per gallon). 55 utilities serving 3.7 million people as they report it, largest first.

All 55, by people served

Illinois utilities with hard water, 1 to 55
Utility	Based in	Serves	Hardness, mg/L	Grains per gallon
Chicago	Chicago	2,721,308	137	8
Waukegan	Waukegan	87,149	140	8.2
Bloomington	Bloomington	79,000	135	7.9
Decatur	Decatur	76,122	130	7.6
Schaumburg	Schaumburg	75,750	132	7.7
Evanston	Evanston	74,486	130	7.6
Oak Lawn	Oak Lawn	58,362	140	8.2
Hanover Park	Hanover Park	37,470	135	7.9
Vernon Hills - Lake Co Pw	Vernon Hills	33,207	130	7.6
Gurnee	Gurnee	30,193	152	8.9
Highland Park	Highland Park	30,176	140	8.2
Aqua Illinois - Vermilion County	Danville	30,106	130	7.6
Aqua Illinois - North Maine Utilities	Glenview	30,043	130	7.6
Wilmette	Wilmette	27,650	135	7.9
Great Lakes Naval Training Station	North Chicago	23,000	130	7.6
South Holland	South Holland	22,000	140	8.2
Lake Forest	Lake Forest	19,642	140	8.2
IL American - Streator	Streator	19,000	173	10.1
Round Lake	Round Lake	18,430	140	8.2
North Chicago	North Chicago	16,813	130	7.6
Wildwood Subdivision - Lake Co Pw	Libertyville	14,073	130	7.6
Western Springs	Western Springs	13,629	131	7.7
Lincolnwood	Lincolnwood	13,463	136	8
Glen Carbon	Glen Carbon	12,618	122	7.1
Winnetka	Winnetka	12,475	140	8.2
IL American - Pontiac	Pontiac	11,864	154	9
Clear Water Service Corp	Mattoon	8,900	170	9.9
Glencoe	Forest Park	8,849	140	8.2
Mascoutah	Mascoutah	8,759	147	8.6
Chester	Chester	8,407	135	7.9
Vandalia	Vandalia	7,616	130	7.6
Southeast Regional Water Facility	Darien	6,940	124	7.2
Litchfield	Litchfield	6,648	155	9.1
Pinckneyville	Pinckneyville	5,804	130	7.6
Staunton	Staunton	5,756	150	8.8
Wilmington	Wilmington	5,700	155	9.1
Monticello	Monticello	5,548	160	9.4
Highwood	Highwood	5,335	135	7.9
Anna	Anna	4,910	137	8
Watseka	Watseka	4,767	150	8.8
Sullivan	Sullivan	4,729	140	8.2
Eldorado	Eldorado	4,715	172	10.1
Freeburg	Freeburg	4,707	159	9.3
Pittsfield	Pittsfield	4,697	180	10.5
Dupo	Dupo	4,684	150	8.8
Sparta	Sparta	4,395	140	8.2
Millstadt	Millstadt	4,071	178	10.4
Fairbury	Fairbury	3,633	140	8.2
Hainesville	Hainesville	3,528	160	9.4
Carlyle	Carlyle	3,373	161	9.4
Pontoon Beach PWD	Pontoon Beach	3,325	134	7.8
Southern IL University - Edwardsville	Edwardsville	2,817	129	7.6
Mount Olive	Aviston	2,193	130	7.6
Blandinsville	Blandinsville	569	150	8.8
Buckley	Buckley	500	160	9.4

Source: Illinois Environmental Protection Agency, Bureau of Water, 327 utilities, results from Aug. 2, 2016 to July 29, 2026, read Oct. 17, 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.

All 55, by people served

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