Illinois Water Quality Rankings 2026: Best & Worst Cities

This page ranks the 56 Illinois cities whose water systems we have matched to EPA records. Every city starts at 100 points and loses points for health-based EPA violations in the last five years (SDWIS 2026Q2), its most recent Lead and Copper Rule 90th-percentile result, PFAS detected in EPA's 2023–2026 UCMR5 monitoring, and 2012–2019 compliance samples that averaged near or above a limit. Letters follow fixed bands (A ≥90, B ≥80, C ≥70, D ≥60, F below 60). Cities run from the highest score (Champaign) down to the lowest (Calumet City); ties are ordered by population served. See the full scoring methodology for every deduction and the data vintages. 4 further Illinois cities are listed at the bottom without a grade because we have not yet matched them to an EPA water system.

What your city's grade means

An A or B grade points to water that consistently tests within federal safety limits, while a C suggests moderate issues worth watching and a D or F flags contaminants or compliance problems serious enough to act on. These grades describe system-level water leaving the treatment plant — they can't account for your home's own plumbing, so older houses with lead service lines or fixtures can add contaminants after the water arrives. For a contaminant-by-contaminant view, see the Illinois contaminant breakdown or drill into the county-level rankings.

What Illinois residents should do

• Find your city in the ranking below and open its full report for its violation history, lead results and PFAS table.
• See how Illinois compares against the best-rated and worst-rated cities nationwide.
• Test your home's water if you have concerns — the most common issues involve lead, PFAS, and arsenic.
• Check whether your utility still has lead service lines in Illinois — EPA's inventory counts lead pipes by water system, a risk that plant-level grades cannot capture. Read the lead guide for testing and filter options.
• If treatment makes sense for your situation, compare certified water filters matched to the contaminants found in your area.

We track 60 cities in Illinois. 56 of them are matched to an active EPA-registered community water system (PWSID). Those 56 systems report serving 6,217,785 people in EPA's Safe Drinking Water Information System (SDWIS).

Of 56 cities of the 60 Illinois cities we can grade from EPA records, 47 cities (84%) grade B or better, 5 sit in the C range and 4 grade D or F. The average score is 90/100. 4 cities are not graded because they have not been matched to an EPA system yet.

EPA records 5 health-based violations in the last five years across 4 cities, and 1 city still has a health-based violation listed as unresolved. Monitoring and reporting violations (140 in the same window) are paperwork lapses and cost far fewer points.

56 cities have a Lead and Copper Rule 90th-percentile result from 2020 or later: 3 cities at or above the 15 ppb action level, 29 cities at 5 ppb or more.

EPA's UCMR5 PFAS monitoring (2023–2026) covers 56 cities: PFAS were detected in 17 cities, and PFOA or PFOS reached EPA's 4 ppt limit in 2 cities.

Algonquin scores highest (100) and Calumet City lowest (55), a 45-point spread.

Lead pipes are the part of tap-water risk a treatment-plant grade cannot see, so start with EPA's service line inventory (Q2 2026 snapshot). 2,202 Illinois systems inventoried 3,875,591 service lines: 615,181 confirmed lead plus 57,081 galvanized lines requiring replacement, spread across 329 systems. Another 530,644 lines (14%) are still of unknown material, which EPA counts as possible lead until verified.

Of the 56 city-linked Illinois utilities with an inventory on file, 43 report at least one lead or galvanized-requiring-replacement line and 13 report no lead with most lines verified. The largest, CHICAGO (Chicago, 2,721,308 served), reports 350,531 lead lines and 10,326 galvanized requiring replacement.

Illinois's guide on this site singles out lead, atrazine, nitrates, and radium. Lead (EPA action level 0.015 mg/L (15 ppb); health goal 0) harms brain development in children and raises blood pressure and kidney risk in adults; Atrazine (EPA MCL 0.003 mg/L) is associated with cardiovascular and reproductive effects; Nitrate (EPA MCL 10 mg/L (as nitrogen)) can cause methemoglobinemia ("blue baby syndrome") in infants under six months; Radium (EPA MCL 5 pCi/L (combined radium-226/228)) increases cancer risk with long exposure.

Where a system draws its water shapes which of these show up. Radium is naturally occurring and tends to show up in groundwater, leaching from bedrock into aquifers rather than arriving from pollution. Atrazine and nitrate follow fertilizer, manure and septic loading, so they are most often a concern for systems drawing shallow groundwater in farm regions. PFAS and chromium are tied to specific sites — industrial discharges, firefighting-foam use at airports and bases — rather than to geology, so contamination is local and can affect either source type. Lead is different again: it enters after treatment from service lines and household plumbing, which is why the inventory figures above matter more than plant-level results. The Consumer Confidence Report your Illinois utility mails each year states whether your system draws surface water or groundwater.

The best water quality in Illinois is found in Champaign with a score of 100/100 and a grade of A. This puts Champaign among the top-performing cities in the country for drinking water safety.

The most concerning water quality is in Calumet City scoring 55/100 with a grade of F. Residents may want to consider home water testing and filtration options.

The statewide average score is 90/100, which is 2 points above the national average of 88/100. Over half (68%) of Illinois cities score above the national average, though some areas face challenges.