Illinois Private Well Water Quality 2026

Illinois PFAS Contamination and Private Wells

Illinois is one of the most PFAS-contaminated states in the country. A Chicago Tribune analysis identified over 1,600 potential industrial sources of PFAS in Illinois — more than almost any other state. More than 60 percent are concentrated in Chicago and its suburbs, but there is at least one potential industrial source in 85 of the state’s 102 counties. For decades, there were no enforceable limits on PFAS in Illinois groundwater. That changed in April 2025, when the Illinois Pollution Control Board adopted Part 620 groundwater quality standards for six PFAS compounds — including PFOA, PFOS, PFNA, PFHxS, PFBS, and HFPO-DA.

The immediate consequence was stark. The Illinois EPA notified 47 community water systems that their groundwater exceeded the new standards, with a further 10 emergency-connected systems also flagged — 57 in total. The Illinois Department of Public Health (IDPH) then issued guidance advising private well owners near those systems to test their water, because groundwater does not respect the boundary between public and private supply. Private wells in the same geological zone are drawing from the same aquifer.

The new state standards for PFOA and PFOS align broadly with the 2024 federal MCLs of 4 ppt each, which apply to community water systems. Those federal standards do not cover private wells — meaning private well owners in Illinois have no legal protection and no mandatory notification if their water is contaminated.

Key PFAS-affected areas in Illinois include:

• Crest Hill, Will County — in mid-2025, the city was among those notified by Illinois EPA of PFAS exceedances in its community wells, with PFOA detected at 13.7 ppt (over three times the federal limit of 4 ppt) and PFHxS at 12.2 ppt. Private wells in surrounding areas draw from the same groundwater.
• Rockford, Winnebago County — a Chemtool lubricant factory explosion in 2021 released PFAS-laden firefighting foam across the area. State investigators found some of the highest PFAS concentrations recorded in Illinois in nearby private wells, though persuading residents to test proved difficult even when testing was offered for free.
• Rockton, Winnebago County — adjacent to the Chemtool site and also within the Southeast Rockford Superfund area, several private wells are known to be contaminated. The area has been subject to routine well testing since the 1980s due to historic industrial solvent contamination.
• Downers Grove, DuPage County — the Ellsworth Industrial Park Superfund site involved VOC contamination from industrial solvents that migrated into private drinking water wells in unincorporated areas. Around 800 homes were connected to the public supply in 2004; some surrounding properties remain on private wells.
• Chicago suburbs broadly — over 1,000 of Illinois’ 1,600+ identified PFAS source facilities are in the Chicago metro area. Private wells in unincorporated portions of suburban Cook, DuPage, Kane, Lake, McHenry, and Will counties face elevated risk.

Nitrate Contamination in Illinois Well Water

Illinois is one of the most heavily farmed states in the US, and that agricultural intensity has a direct impact on private well water quality. Nitrate from fertiliser runoff is a documented risk for well owners across central and north-central Illinois. The USGS classifies the Midwest as a high-risk region for nitrate groundwater contamination due to high nitrogen input from agriculture and well-drained soils that allow nitrates to migrate readily to the water table.

A report from Prairie Rivers Network found widespread nitrate contamination in Illinois groundwater, with some areas reaching levels up to nine times the EPA’s safe drinking water standard of 10 mg/L — among the highest in the country. The Illinois EPA identifies shallow sand point wells and large-diameter dug wells as the most vulnerable to nitrate contamination, particularly those near farmland, manure storage areas, or feedlots.

Nitrate is colourless, odourless, and tasteless. Boiling water does not remove it — it can actually concentrate it. High nitrate levels are especially dangerous for infants under six months, pregnant women, and people with certain health conditions. Standard carbon pitcher filters also do not remove nitrate. Reverse osmosis, distillation, or ion-exchange systems are required.

There is an additional PFAS-related agricultural risk unique to Illinois. A Chicago Tribune investigation found that over 615,000 tons of PFAS-contaminated sewage sludge from the Metropolitan Water Reclamation District of Greater Chicago was spread on approximately 29,000 acres of Illinois farmland over a six-year period. Fields in Fulton, Kankakee, and Will counties were found to contain PFAS at levels exceeding EPA guidelines designed to protect groundwater. This sludge-to-soil-to-groundwater pathway creates a contamination risk for private wells in those agricultural areas that goes beyond standard industrial PFAS sources.

Arsenic, Radium, and VOCs in Illinois Groundwater

Beyond PFAS and nitrate, Illinois well owners face three additional naturally occurring and industrial contaminant risks.

Arsenic is present in groundwater statewide, with naturally elevated levels in southern Illinois where deep sandstone aquifers contain higher geological concentrations. Arsenic has no smell or taste and can only be identified through laboratory testing. Long-term exposure above 10 ppb is linked to multiple cancers, cardiovascular disease, and nerve damage.

Radium is a naturally occurring radioactive element found primarily in the northern third of Illinois, within deep bedrock aquifers. The Illinois EPA identifies radium as a significant concern for deep private wells in this region, and it has been detected in private well water. Testing is the only way to identify its presence. Radium cannot be detected by taste, smell, or sight.

Volatile organic compounds (VOCs) — including trichloroethylene (TCE) and tetrachloroethylene (PCE) — are a documented risk in areas near industrial sites. The Downers Grove and Rockford Superfund sites are the clearest examples: industrial solvents contaminated private wells in unincorporated residential areas near industrial parks. VOCs are also used as solvents, degreasers, and dry-cleaning chemicals, and can persist in groundwater for decades. If your well is in or near an industrial area, urban corridor, or known Superfund site, VOC testing is warranted.

Coliform bacteria are a risk statewide, particularly in older, shallow, or poorly maintained wells, and in areas with failing or inadequate septic systems. The Illinois EPA recommends annual testing for coliform bacteria for all private well owners.

Regulatory Situation for Illinois Well Owners

Private wells in Illinois are not regulated under the Illinois Safe Drinking Water Act. The state has no authority to mandate testing of private residential wells, and there is no routine monitoring or notification system for well owners. Testing and treatment is entirely the responsibility of the individual homeowner.

The 2025 Part 620 PFAS groundwater standards are a significant step forward, but they apply to community water systems, not private wells. The state’s Right-to-Know laws require community systems to notify customers when groundwater standards are exceeded — but private well owners adjacent to those systems receive no automatic legal notification. The May 2025 IDPH advisory recommending private well testing near flagged community water systems was guidance, not a legal requirement.

Check our Illinois municipal water quality page for city-by-city tap water data, or use our live boil water notice tracker for active advisories across the state.

Known High-Risk Areas in Illinois

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Illinois Well Water — and What to Do Next

Given Illinois’ contamination profile — PFAS, nitrate, arsenic, radium, and VOCs — every private well owner in the state should test their water. The IDPH recommends annual testing for coliform bacteria and nitrate as a baseline. For PFAS, a one-time test is recommended for all well owners, and should be treated as urgent if you are near a flagged community water system, an industrial zone, an airport, or a military facility.

Contact your local county health department or use the IDPH certified lab finder at dph.illinois.gov. The Illinois EPA PFAS Interactive Dashboard allows you to check whether community water systems near you have recorded PFAS detections. You can also check the list of 57 flagged community water systems — published by Illinois EPA — to determine whether you are in a potentially affected groundwater zone.

For filter options, our well water filter guide covers reverse osmosis systems for PFAS and arsenic, ion-exchange for nitrate and radium, UV disinfection for bacteria, and whole-house well systems for comprehensive treatment. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For Midwest well water neighbours with similar risk profiles, see our pages on Michigan wells, Wisconsin wells, and Iowa wells. Return to the private well water directory to find your state.