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Water quality

Illinois water quality

Illinois public water is regulated by the Illinois EPA and generally meets federal standards, but the state faces two well-documented challenges. According to the US EPA and Illinois EPA, Illinois has more lead service lines than any other state, roughly one million, with Chicago alone accounting for the most of any US city. According to EWG and Illinois EPA data, nitrate from agricultural runoff also affects many smaller community systems.

Documented considerations

Lead

According to the US EPA, Illinois has about one million lead service lines, the most of any state, and Chicago has the most of any city (the city estimates roughly 412,000 of its lines are known or suspected to contain lead).

Nitrate

According to EWG analysis of state data, elevated nitrate from fertilizer and manure runoff was detected in the tap water of 217 Illinois communities serving close to 1.9 million people, with contamination worsening in many smaller rural groundwater systems.

PFAS

A 2021 Illinois EPA statewide investigation sampled finished drinking water at over 1,400 entry points and found PFAS in a number of systems, with the agency later notifying multiple community water systems of detections exceeding state groundwater standards.

Hardness

Much of Illinois, which relies heavily on groundwater and Great Lakes sources, reports moderately hard to hard water. Hardness is an aesthetic and scale concern rather than a health hazard.

EPA compliance snapshot

From the EPA ECHO Safe Drinking Water Act database, Illinois community water systems carrying one or more violations on record:

481
systems with a violation on record
12
with a health-based violation
9
flagged serious violators

Most common violation categories

  • Revised Total Coliform Rule (185)
  • Nitrate (149)
  • Public Notice (118)
  • Lead and Copper Rule (71)
  • Total Haloacetic Acids (HAA5) (70)
  • TTHM (69)

Counts are public EPA ECHO figures. 'Health-based' means a system carries at least one health-based violation flag in ECHO. A violation on record is not a statement that current tap water is unsafe; most systems return to compliance. Always check your utility's Consumer Confidence Report for current status. Source: EPA ECHO, retrieved 2026-06-01.

Certified filters for Illinois's main concerns

FAQ

Does Chicago have lead pipes?
Yes. According to the US EPA, Chicago has the most lead service lines of any US city, with the city estimating roughly 412,000 lines that are known or suspected to contain lead. Chicago was granted an extended timeline under federal rules to replace them.
Is nitrate a problem in Illinois drinking water?
In farm-belt communities it can be. According to EWG analysis of state testing, elevated nitrate from agricultural runoff was found in 217 Illinois community water systems serving nearly 1.9 million people. Nitrate above 10 mg/L is a regulated health concern.
How do I know if my Illinois home has a lead service line?
Under the Illinois Lead Service Line Replacement and Notification Act, water systems are inventorying and reporting lead lines, and the Illinois EPA maintains lead service line information for the public. Contact your water utility for your address-specific status, and consider lead-certified filtration as an interim measure.

Sources

  1. EPA - Chicago Lead in Drinking Water Study
  2. Illinois EPA - Lead Service Line Information
  3. EWG - Nitrate in Illinois Tap Water
  4. Illinois EPA - PFAS Statewide Investigation

Not sure how to read your local report? See our guide on reading a water quality report.