St. Clair County, Illinois — public water systems

42 active public water systems serve St. Clair County, reporting 255.5K people served.

Dataset updated October 2026 . Source: EPA SDWIS/ECHO, refreshed quarterly.

Active systems

Population served

255.5K

Community systems

Groundwater share

31%

Water systems in St. Clair County

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Active public water systems in St. Clair County, Illinois
#	Water system	County	Population served	Type	Source
1	Il American-East St Louis	St. Clair	131,368	Community	Surface water
2	O Fallon	St. Clair	46,603	Community	Purchased surface water
3	Caseyville	St. Clair	13,798	Community	Purchased surface water
4	Cahokia Heights	St. Clair	12,528	Community	Purchased surface water
5	Mascoutah	St. Clair	8,759	Community	Purchased surface water
6	American Water Oper and Maintenance, LLC	St. Clair	6,779	Community	Purchased surface water
7	Lebanon	St. Clair	4,714	Community	Purchased surface water
8	Freeburg	St. Clair	4,707	Community	Purchased surface water
9	Dupo	St. Clair	4,684	Community	Groundwater
10	Smithton	St. Clair	4,381	Community	Purchased surface water
11	Millstadt	St. Clair	4,071	Community	Purchased surface water
12	New Athens	St. Clair	1,970	Community	Purchased surface water
13	Marissa	St. Clair	1,921	Community	Purchased surface water
14	Prairie Dupont PWD	St. Clair	1,863	Community	Purchased surface water
15	Mound PWD	St. Clair	1,500	Community	Groundwater
16	St Libory	St. Clair	628	Community	Groundwater
17	Lenzburg	St. Clair	616	Community	Purchased surface water
18	Valley View Estates	St. Clair	580	Community	Purchased surface water
19	Southwestern Il Correctional Center	St. Clair	563	Community	Purchased surface water
20	Fayetteville	St. Clair	490	Community	Purchased surface water
21	Meadowbrook Mh Community, LLC	St. Clair	463	Community	Purchased surface water
22	S L M Water Commission	St. Clair	385	Community	Surface water
23	Arapaho Village MHP	St. Clair	368	Community	Purchased surface water
24	Summerfield	St. Clair	347	Community	Purchased surface water
25	Fsh Water Commission	St. Clair	313	Community	Purchased surface water
26	Ildu Lepere MHP, LLC	St. Clair	250	Community	Purchased surface water
27	Karbans Knotty Pines	St. Clair	200	Transient non-community	Groundwater
28	St Clair County Foley Park	St. Clair	200	Transient non-community	Groundwater
29	St Michaels Church	St. Clair	50	Transient non-community	Groundwater
30	Children of Promise	St. Clair	50	Non-transient non-community	Groundwater
31	Twice the Ice Freeburg	St. Clair	50	Transient non-community	Purchased surface water
32	New Athens Hanft Pk Larry Webe	St. Clair	30	Transient non-community	Groundwater
33	Walmart Supercenter 201	St. Clair	30	Transient non-community	Purchased surface water
34	Twice the Ice Lebanon	St. Clair	25	Transient non-community	Purchased surface water
35	Quail Restoration Association	St. Clair	25	Transient non-community	Groundwater
36	Schnucks 177 O Fallon	St. Clair	25	Transient non-community	Purchased surface water
37	Millstadt Sportsmans Club	St. Clair	25	Transient non-community	Groundwater
38	Freeburg Ice Man	St. Clair	25	Transient non-community	Purchased groundwater
39	Twice the Ice St Libory	St. Clair	25	Transient non-community	Purchased groundwater
40	New Baden Market Center	St. Clair	25	Transient non-community	Purchased groundwater
41	Schnucks 205 Belleville	St. Clair	25	Transient non-community	Purchased surface water