Water in Illinois.
Chicago and most of northeast Illinois drink Lake Michigan water — among the highest-quality source water in the country. Yet Chicago has more lead service lines than any U.S. city. Disinfection byproducts are widespread on Mississippi River systems downstate.
Chicago has an estimated 400,000+ lead service lines — more than any U.S. city.
How Illinois regulates drinking water.
Federal SDWA primacy. Lead Service Line Replacement Act (2021) requires full replacement of all lead service lines by 2042 — most aggressive state mandate in the country.
Illinois Environmental Protection Agency — Bureau of Water
Illinois's water history, in order.
The contamination events, regulatory shifts, and major settlements that define how this state thinks about drinking water today.
- 2016
Post-Flint lead testing identifies elevated lead in 70+ Chicago Public Schools.
- 2021
Illinois Lead Service Line Replacement Act mandates full replacement by 2042.
- 2024
Federal LCRI replaces line replacement by 2034; Illinois extends its statutory deadline.
The actual water you drink.
The physical rivers, aquifers, lakes, and reservoirs that feed Illinois's public water systems. Source quality is the foundation of tap quality — and where the long-term protection fights happen.
- lakeLake Michigan
Chicago and most NE Illinois — among the best municipal source water in the U.S.
- riverMississippi River
Quad Cities, downstate.
- aquiferCambrian-Ordovician Aquifer
Far western IL, NW Chicago suburbs.
- aquiferMahomet Aquifer
Central IL sole-source aquifer.
Source-water mix
~75% surface water (Lake Michigan), ~25% groundwater
Major cities served
Chicago · Aurora · Joliet · Naperville · Rockford · Springfield
Who actually serves the water.
The largest public water systems in Illinois by population served. Click your ZIP after to see the full live EWG report for your specific utility.
- Chicago Department of Water ManagementChicago2,700Kserved
- Aurora Water and Wastewater DepartmentAurora200Kserved
- Springfield Water DepartmentSpringfield115Kserved
Where the contamination comes from.
Every state has a different industrial fingerprint. The industries below are the dominant historical and active contamination sources in Illinois's drinking water systems.
Pre-1986 Chicago and downstate housing accounts for ~1.05 million lead service lines statewide — the largest count in the U.S. Coal-ash impoundments at multiple Illinois Power sites threaten groundwater. East St. Louis legacy industrial contamination persists.
What state data flags most consistently.
Drawn from EPA SDWIS sampling records, EWG state summaries, and regional regulatory action over the past five years. Read the full deep dive on each.
Lead
A neurotoxic metal that leaches from old pipes and solder. No safe level for children.
Trihalomethanes (TTHMs)
Byproducts of chlorinating water. Linked to bladder cancer at chronic exposure.
PFAS (Forever Chemicals)
A class of ~15,000 synthetic chemicals that don't break down. Now regulated for the first time.
Chromium-6 (Hexavalent Chromium)
The Erin Brockovich chemical. A known carcinogen with no federal-specific limit yet.
Risk isn't evenly distributed.
Chicago residents in pre-1986 buildings face the highest lead exposure in the U.S. by absolute number of lead service lines.
Illinois has roughly 1.05 million lead service lines statewide; Chicago alone has ~400,000.
~12% on private wells, concentrated downstate.
What's coming for Illinois's water.
Great Lakes warming drives toxic algal blooms in southern Lake Michigan and Mississippi River. Combined sewer overflow events from intense rainfall affect Chicago intakes. Mahomet Aquifer drawdown is accelerating under industrial and agricultural demand.
Statewide mandate
PA 99-0922 (2017) requires all IL schools serving pre-K through 5 to test for lead. Results publicly available via the IL State Board of Education.
Five questions for your next Consumer Confidence Report.
Your utility is required to send you a Consumer Confidence Report annually. Most are dense and procedural. These are the questions worth following up on for Illinois specifically.
- 1
When is my home scheduled for lead service line replacement under the 2042 mandate?
- 2
Has my school district published its PA 99-0922 lead test results?
- 3
Does my utility draw from Lake Michigan or a downstate source?
- 4
Has my system had any harmful algal bloom advisories?
Most state regulators allow public records requests for the underlying lab reports behind your CCR — your utility should be able to provide them on request.
What's changed in Illinois water law.
Drinking water regulation moves at the state level as much as the federal level. Below are notable recent bills and regulatory actions specific to Illinois.
- 2024
Federal LCRI accelerates IL replacement timeline; state continues with 2042 statutory deadline.
- 2021
SB 119 — Lead Service Line Replacement Act mandates full replacement by 2042 (most aggressive in U.S.).
- 2017
PA 99-0922 — School Lead Testing mandate.
For lead, NSF/ANSI 53 carbon block certified for lead reduction. Pitcher filters labeled "lead" reduction are the cheapest path — replace cartridges on schedule.
We don't recommend brands — the NSF/ANSI certification number matters more than the name on the box.
This is the state. Your address is the answer.
State-level patterns don't tell you about your specific tap. Run your ZIP for the live EWG contaminant report on your utility — or build a personalized Water File for your household.
Source-water mix, utility counts, lead-service-line estimates, and private-well shares are approximate, drawn from EPA SDWIS public data and state primacy-agency summaries. Contaminant rankings reflect EWG state-level monitoring data and regional regulatory action — they are not exhaustive. Timeline events are publicly documented. See methodology for the full sourcing. Search EPA SDWIS for Illinois