Water quality · Illinois
Water quality in Illinois
Water quality (EPA SDWIS) data for ZIP codes in Illinois. Pick a ZIP below to dive into the water quality summary.
Last verified 2026-05-13 · methodology
What lands here
Pages show the CWS serving the address, any health-based violations in the last 3 years, most recent lead and copper sampling result, and a link to the primary SDWIS record.
Source & refresh
EPA SDWIS. Refreshed quarterly (federal mandate). Primary source →
Illinois top concern
Lead service lines, flooding (Mississippi/Illinois)
Illinois has the highest LCRR lead-service-line replacement obligations in the US (Chicago alone >400,000 LSLs). FEMA AE coverage extends along the Mississippi, Illinois, and Rock rivers. EPA SDWIS shows urban vs. downstate disparity.
See Illinois state page for the full state-level rollup across all 12 dimensions.
Read more on water quality
Editorial deep-dives explaining the source data, its limits, and how to read it.
Flood zones explained — what AE, X, and VE actually mean
Plain-English guide to FEMA flood-zone codes (A, AE, AH, V, VE, X, X-shaded). What the 1% and 0.2% annual-chance zones mean for your property and your insurance.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
Lead and Copper Rule 2024 — the federal lead-pipe inventory mandate
The 2024 Lead and Copper Rule Revisions (LCRR) require every US community water system to inventory and report lead service lines. Plain-English guide.
AQI explained — what 50, 100, 150 actually mean for your lungs
Plain-English guide to the EPA Air Quality Index (AQI) and the 6 categories from Good to Hazardous. When to take precautions and which pollutants matter.
8 Illinois ZIPs
ZIP 60601
Chicago, IL
Water quality →
ZIP 60614
Chicago (Lincoln Park), IL
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ZIP 61602
Peoria, IL
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ZIP 60302
Oak Park, IL
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ZIP 60611
Chicago (Streeterville), IL
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ZIP 61820
Champaign, IL
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ZIP 60201
Evanston (IL), IL
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ZIP 60515
Downers Grove, IL
Water quality →