Water Quality Technical Report — CHICAGO, IL
- PWSID
- IL0316000
- Population
- 2,721,308
- Source
- Surface Water
- Data Period
- —
- Last Updated
A note from the author — I'm Jacob Thorwolf. WaterAdvantage.org is a personal project of mine, separate from my day job as an Account Executive at Bottleless Nation, a commercial water filtration company. If you request a consultation through any form on this site, it comes to me or a colleague at BN. More about this project →
Summary
CHICAGO serves approximately 2,721,308 people in CHICAGO, Illinois. Based on contaminant analyses from DNR, EPA ECHO, EPA UCMR5, 0 contaminants have been measured above federal EPA standards (MCL) and 2 exceed health-based guidelines. The most significant finding is Lead (90th Percentile) at 0.007 mg/L, which is 35x the health guideline. Data is drawn from source-level compliance monitoring and covers 2018 through 2026. Results reflect conditions at the point of collection (wells, treatment plants), not necessarily at the tap.
Key Findings
- Lead (90th percentile): Below the legal limit but above health-based guidelines (2026 reading). From your water system's testing.
- Arsenic: Below the legal limit but above health-based guidelines (2026 reading). From your water system's testing.
Understanding the two thresholds
EPA Legal Limit (MCL)
The highest level of a contaminant allowed by federal law. Utilities that exceed this threshold face enforcement action. Limits balance health risk against the cost of treatment, so they are not always set at levels considered safe by independent researchers.
Health Guideline
The level below which independent researchers (CalEPA, WHO, EWG) believe there is no known health risk. Guidelines are not legally enforceable but are typically stricter than legal limits — often by 10x or more for contaminants like arsenic and lead.
A reading can be below the EPA limit (legally compliant) while still exceeding health guidelines (above levels considered safe by independent researchers).
Exceeds Health Guidelines
These contaminants were detected below the EPA legal limit but above a health-based guideline from a public health agency (CalEPA OEHHA, WHO, or similar). Health guidelines are non-enforceable research-backed targets that are often stricter than the legal limit.
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Arsenic Skin damage, circulatory problems, increased risk of cancer | 640 | ng/L | 4 | 10000 | DNR | |
| Lead (90th Percentile) Developmental delays in children, kidney damage, high blood pressure. There is no safe level of lead exposure. | 7 | ug/L | 0.2 | 15 Pending rule: LCRI 2024 — Action level drops from 15 → 10 µg/L effective 2027; full lead service line replacement within 10 years (EPA Lead & Copper Rule Improvements, October 2024) | EPA ECHO |
Microplastics
Microplastics have been documented in raw and treated drinking water worldwide, but federal regulations do not currently require testing — so there is no data specific to this system. Standardized methods and rules are in progress.
Other Regulated Contaminants
These contaminants were detected within federal standards (EPA Maximum Contaminant Levels). They are presented for transparency.
Total Trihalomethanes (TTHMs) (LRAA): 25.25 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT6, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 22.60 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH7, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 23.78 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT2, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 21.80 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH3, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 20.05 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT5, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 21.40 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH1, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 21.00 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT3, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Total Trihalomethanes (TTHMs) (LRAA): 21.40 ug/L — within limit of 80 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH2, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 13.00 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT6, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.95 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH7, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 12.27 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH3, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.98 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT5, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.80 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH1, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.10 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT3, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.43 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HT2, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
Haloacetic Acids (HAA5) (LRAA): 11.40 ug/L — within limit of 60 ug/L
EPA Stage 2 DBPR — Locational Running Annual Average, monitoring point Well S2HH2, based on 4 samples across 4 quarters (2025Q3 · 2025Q4 · 2026Q1 · 2026Q2).
Disinfection byproducts are regulated as a running average under Stage 2 DBPR, not as individual samples. A single sample exceeding the MCL is not itself a compliance violation — the annual running average is the enforceable metric.
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Nitrate (as N) Blue baby syndrome in infants | 370 | ug/L | 10000 | 10000(as N) | DNR | |
| Combined Radium (226+228) Increased risk of cancer | 0.5 | pCi/L | 0 | 5 | DNR | |
| Barium Increase in blood pressure | 19.1 | ug/L | 1000 | 2000 | DNR | |
| Fluoride (natural) Bone disease, mottled teeth in children | 750 | ug/L | 4000 | 4000 | DNR |
Unregulated Detected Contaminants
These contaminants were detected but do not have a federal Maximum Contaminant Level. They are monitored for awareness, not compliance.
Other Substances
| Contaminant | Result | Unit | Health Guideline | EPA Legal Limit | Source | Sample Date |
|---|---|---|---|---|---|---|
| Copper (90th Percentile) Gastrointestinal distress at high levels. Long-term exposure can cause liver or kidney damage. Per-source breakdown (100 sampling locations)
| 13 | ug/L | 300 | 1300 | DNR |
Other Potential Contaminants
Not detecting a contaminant does not prove it isn't present — it only means the laboratory didn't test for it, or tested below the reporting limit. Many substances of emerging concern are not routinely monitored because federal regulations haven't caught up to the science.
- Pharmaceuticals and personal care products (PPCPs) — USGS Emerging Contaminants program · Kolpin et al. (USGS FS-2006-3013)
- Unregulated PFAS compounds — EPA PFAS rule (2024) · EPA UCMR monitoring
- 1,4-Dioxane — EPA technical fact sheet
- Hexavalent chromium (Cr-VI) — EPA chromium in drinking water · California OEHHA PHG
- Unregulated disinfection byproducts — EPA Stage 1 / Stage 2 DBPR
- Endocrine disruptors — EPA Endocrine Disruptor Screening Program
Compliance History
Formal EPA and DNR compliance events on record for this utility. Includes all events from the last 10 years plus any unresolved violations regardless of age. Health-based violations are legally enforceable thresholds that were exceeded; procedural events are monitoring or reporting lapses that don't indicate contamination by themselves.
Jul 2, 2025 – ongoing
May 1, 2025 – May 31, 2025
Apr 1, 2025 – Apr 30, 2025
Jan 1, 2025 – Dec 31, 2025
Jul 1, 2024 – Sep 30, 2024
Dec 30, 2021 – ongoing
Jul 1, 2021 – ongoing
Jul 1, 2020 – ongoing
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
Jan 1, 2019 – Dec 31, 2019
+ 25 older events in the 10-year window not shown
Source: EPA ECHO enforcement and violation records (via Envirofacts / SDWIS Federal Reports).
Action Steps
This system has contaminants above a legal limit or multiple health guidelines. The following steps are concrete things a homeowner or facility operator can do right now — starting with the most important non-commercial options.
- Request the utility's Consumer Confidence Report (CCR). The CCR compares utility-reported readings to the federal legal limits and is independent of this site. Utilities must make it available on request. EPA CCR search.
- Get a certified tap test. A state-certified laboratory can test your tap for a specific contaminant or a broader panel. A single-contaminant test runs in the low tens of dollars; a comprehensive panel runs several hundred. Ask for the EPA-certified lab list from the Illinois drinking water program. State lab certification programs.
- Consider point-of-use filtration. For the specific contaminants detected in this system, the exceedance sections above list the technology categories (reverse osmosis, granular activated carbon, ion exchange, etc.) that target each class. Those are category-level descriptions — the right choice depends on the contaminant profile, budget, and installation constraints.
- Contact the utility directly. Ask about the specific contaminants you're concerned about and request the most recent sampling data. The EPA SDWIS portal lists utility contact details. EPA SDWIS system lookup.
- Check the utility's lead service line inventory. Under the Lead and Copper Rule Revisions (LCRR, 2024), utilities must publish a service line inventory identifying lines flagged as lead, galvanized-requiring-replacement, or unknown material. If your service line is flagged or unknown, the utility is required to replace it on a scheduled timeline. EPA Lead and Copper Rule Improvements.
Frequently Asked Questions
What contaminants are in CHICAGO water?
Based on available public monitoring data, 39 contaminants have been tested in CHICAGO's water supply. 9 were detected above reporting limits. The most notable detections include Haloacetic Acids (HAA5), Total Trihalomethanes (TTHMs), Nitrate (as N). This data comes from source-level compliance monitoring at wells and treatment plants.
Does CHICAGO water meet EPA standards?
Based on available public monitoring data, no contaminants were measured above federal EPA standards in recent compliance monitoring. However, 2 contaminants exceed independent health guidelines, which are often stricter than legal limits. This assessment is based on source-level monitoring data (wells and treatment plants), not tap-level measurements.
Is CHICAGO, IL water safe to drink?
Based on source-level compliance monitoring, all tested contaminants were within federal standards. However, compliance monitoring tests water at wells and treatment plants, not at individual taps. An on-site test is the only way to know what reaches your tap, as conditions can vary based on plumbing, blending, and distribution.
Does CHICAGO water have lead?
No. CHICAGO's most recent Lead and Copper Rule testing found a 90th-percentile lead level of 0.007 mg/L, which is below the EPA action level of 0.015 mg/L. That means at the systemwide level, lead is not exceeding the enforcement threshold. Lead levels can still vary significantly by individual building — older homes and schools with legacy plumbing can have much higher readings than the system average.
Cross-check against the official record
This report is our read of the public monitoring data. Every Illinoisutility also publishes an annual Consumer Confidence Report (CCR) — a plain-language summary written by the utility itself, usually mailed with a water bill or posted on the utility's website. If anything in this report surprises you, request CHICAGO's latest CCR directly from the utility, or browse the underlying compliance data published by Illinois EPA.
Data Sources and Methodology
- Illinois EPA Compliance Monitoring
State-level drinking water compliance testing. Covers all regulated contaminants for community water systems. Source-level monitoring at wells and treatment plants. Individual result links are provided for each contaminant in the tables above.
- EPA ECHO Lead & Copper Rule
90th percentile measurements from EPA Enforcement and Compliance History Online. Based on tap-level sampling at high-risk sites.
- EPA UCMR5
Unregulated Contaminant Monitoring Rule, Fifth cycle. Per-analyte PFAS results from utility-level sampling.
Definitions
- Maximum Contaminant Level (MCL)
- The highest level of a contaminant allowed in drinking water, set by the EPA. MCLs are legally enforceable standards.
- Maximum Contaminant Level Goal (MCLG)
- The level of a contaminant below which there is no known or expected health risk. MCLGs are non-enforceable public health goals.
- Action Level
- The concentration of a contaminant which, if exceeded, triggers treatment or other requirements. Used for lead and copper.
- Health Advisory
- Non-enforceable guidelines set by the EPA providing information on contaminants that can cause health effects at certain exposure levels.
- Total Dissolved Solids (TDS)
- A measure of all dissolved minerals, salts, and organic matter in water, expressed in mg/L (ppm). Not a health hazard but affects taste and indicates overall mineral content.
- PFAS
- Per- and polyfluoroalkyl substances. A group of manufactured chemicals that do not break down in the environment. The EPA set enforceable limits for several PFAS compounds in 2024.
- Non-Detect (ND)
- The contaminant was tested for but not found above the laboratory's reporting limit. This does not mean zero — it means below the detection threshold.
- VOCs (Volatile Organic Compounds)
- Chemicals that evaporate easily and can contaminate groundwater. Sources include gasoline, industrial solvents, and dry cleaning fluids. Some are regulated by the EPA; many are monitored but not yet regulated.
Download Data
Cite This Report
WaterAdvantage. "Water Quality Technical Report: CHICAGO, IL (IL0316000)." WaterAdvantage.org, 2026-09-06. https://www.wateradvantage.org/report/IL0316000/detail
Curious about filtration for your home or facility? I work at Bottleless Nation during the day and I'm happy to take a look. Submit the form below and I or a colleague will reach out — the consultation is free, and if it turns into a sale, I earn a commission.
Get a free filtration consultation