Illinois utilities whose water varies in hardness.

Water in more than one band, depending on where or when it was sampled: each is given as its range, softest to hardest. 71 utilities serving 1.7 million people as they report it, largest first.

All 71, by people served

Illinois utilities whose water varies in hardness, 1 to 71
Utility	Based in	Serves	Hardness, mg/L	Grains per gallon
Aurora	Aurora	183,000	42 to 122	2.5 to 7.2
IL American - Champaign	Champaign	150,000	40 to 85	2.3 to 5
IL American - East St Louis	East St Louis	131,368	124 to 205	7.3 to 12
Elgin	Elgin	114,797	83 to 128	4.8 to 7.5
Aqua Illinois - Kankakee	Kankakee	80,000	132 to 440	7.7 to 25.7
Normal	Normal	52,736	89 to 560	5.2 to 32.7
Romeoville	Romeoville	50,458	89 to 597	5.2 to 34.9
IL American - Alton	Alton	46,127	132 to 221	7.7 to 12.9
Bartlett	Bartlett	41,500	133 to 638	7.8 to 37.3
Crystal Lake	Crystal Lake	40,661	1.6 to 91	0.1 to 5.3
Dekalb	De Kalb	40,290	110 to 190	6.4 to 11.1
Carpentersville	Carpentersville	37,983	150 to 290	8.8 to 17
Northbrook	Northbrook	34,200	79 to 140	4.6 to 8.2
IL American - Granite City	Granite City	33,572	113 to 224	6.6 to 13.1
St Charles	Saint Charles	33,081	100 to 560	5.8 to 32.7
Lake in the Hills	Lake in the Hills	28,661	12 to 560	0.7 to 32.7
Huntley	Huntley	28,495	19 to 62	1.1 to 3.6
Woodstock	Woodstock	25,630	100 to 250	5.8 to 14.6
South Elgin	South Elgin	23,648	7.7 to 510	0.5 to 29.8
Park Forest	Park Forest	21,687	145 to 200	8.5 to 11.7
East Moline	East Moline	21,374	180 to 220	10.5 to 12.9
Crest Hill	Crest Hill	20,223	7.1 to 618	0.4 to 36.1
Jacksonville	Jacksonville	19,903	120 to 130	7 to 7.6
Lake Zurich	Lake Zurich	19,759	57 to 100	3.4 to 5.8
Shorewood	Shorewood	18,645	71 to 390	4.1 to 22.8
Lemont	Lemont	18,513	52 to 260	3 to 15.2
Ottawa	Ottawa	18,097	2 to 164	0.1 to 9.6
Cary	Cary	17,826	13 to 500	0.8 to 29.2
Morton	Morton	17,117	150 to 250	8.8 to 14.6
Wauconda	Wauconda	15,349	36 to 470	2.1 to 27.5
IL American - Lincoln	Lincoln	15,200	171 to 369	10 to 21.6
Washington	Washington	14,793	89 to 210	5.2 to 12.3
IL American - Sterling	Coleta	14,782	60 to 165	3.5 to 9.6
Lindenhurst	Lindenhurst	14,500	170 to 440	9.9 to 25.7
Rantoul	Rantoul	13,000	94 to 130	5.5 to 7.6
Taylorville	Taylorville	12,806	110 to 180	6.4 to 10.5
Minooka	Minooka	12,800	54 to 283	3.2 to 16.5
Kewanee	Kewanee	12,509	57 to 61	3.3 to 3.6
Richton Park	Richton Park	12,504	150 to 310	8.8 to 18.1
Centralia	Centralia	12,182	160 to 190	9.4 to 11.1
Sugar Grove	Sugar Grove	11,243	0.1 to 520	0 to 30.4
Pingree Grove	Hampshire	10,365	52 to 66	3 to 3.9
Maryville	Maryville	10,150	125 to 470	7.3 to 27.5
Peru	Peru	9,896	114 to 132	6.7 to 7.7
Monmouth	Monmouth	8,902	80 to 470	4.7 to 27.5
Lake Villa	Lake Villa	8,829	93 to 350	5.4 to 20.5
IL American - Jerseyville	Jerseyville	8,412	50 to 63	2.9 to 3.7
Island Lake	Island Lake	8,066	41 to 580	2.4 to 33.9
Princeton	Princeton	7,832	56 to 77	3.2 to 4.5
Hampshire	Hampshire	7,758	55 to 270	3.2 to 15.8
Silvis	Silvis	7,473	179 to 440	10.5 to 25.7
Mendota	Mendota	7,100	162 to 315	9.4 to 18.4
Aqua Illinois - University Park	Pk Forest South	7,002	134 to 485	7.8 to 28.4
American Water Oper and Maintenance, LLC	Scott Air Force Base	6,779	150 to 252	8.8 to 14.7
Curran - Gardner Township PWD	Springfield	6,651	64 to 126	3.8 to 7.4
Volo	Volo	6,629	1.3 to 175	0.1 to 10.2
Carmi	Carmi	6,307	170 to 250	9.9 to 14.6
Fairfield	Fairfield	5,998	100 to 138	5.8 to 8.1
Coal City	Coal City	5,845	26 to 250	1.5 to 14.6
East Alton	East Alton	5,786	90 to 230	5.3 to 13.5
Millstone PWD	Nashville	5,565	44 to 74	2.5 to 4.3
Petersburg	Petersburg	4,725	72 to 196	4.2 to 11.5
Cortland	Cortland	4,398	130 to 300	7.6 to 17.5
Lakewood	Lakewood	4,267	18 to 540	1.1 to 31.6
Saline Valley Conservancy District	Eldorado	3,921	109 to 410	6.4 to 24
Coal Valley	Coal Valley	3,873	111 to 226	6.5 to 13.2
Rend Lake Inter - City Water System	Benton	3,650	55 to 73	3.2 to 4.3
Casey	Casey	3,274	180 to 190	10.5 to 11.1
Nashville	Nashville	3,230	59 to 94	3.4 to 5.5
Bushnell	Bushnell	2,972	50 to 81	2.9 to 4.7
Bookwalter Woods MHP	Gardner	389	84 to 140	4.9 to 8.2

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 71, by people served

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