Public water system · IL0312070
ActiveNorthbrook
At a glance
Northbrook (PWSID IL0312070) is an active community water system in Cook County, Illinois. It reports serving 34,407 people through 12,740 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. EPA's records list 5 violations for this system; 1 is health-based, and the most recent began in July 2023.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
34,407
Service connections
12,740
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Northbrook compare with other water systems in Cook County?
By EPA's size categories, Northbrook is a large system (10,001 to 100,000 people). Cook County has 251 active public water systems. Its population served is about 64% above the county average of 20,993 people per system, and accounts for 0.7% of the 5,269,212 people reported by systems filed under the county. Across Illinois, the 3,872 active systems average 3,204 people each. Nationally, the average active community water system reports serving 6,703 people, so Northbrook is about 5.1 times that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Illinois has 1,773 active community water systems, 46% of the state's 3,872 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 89 Illinois systems (2.3%) list surface water as their primary source.
Who owns and regulates Northbrook?
EPA lists Northbrook as owned by a local government. The IL state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 134 of the 251 active systems in Cook County (53%) are also owned by a local government.
Does Northbrook have drinking water violations?
EPA's records list 5 violations for this system; 1 is health-based, and the most recent began in July 2023. The violations listed here began between June 1977 and July 2023. By type: 4 monitoring and reporting and 1 required treatment not met. The contaminant or rule involved most often is Lead and Copper Rule (2 of them). EPA lists 4 as resolved and 1 as archived. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2023-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2020-12-30 | Monitoring and reportingLead Consumer Notice · code 66 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2003-12-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 1993-01-01 | Required treatment not metPublic Education · code 65 | Lead and Copper Rulecode 5000 | Yes | Resolved |
| 1977-06-30 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Archived |
All 5 violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Northbrook: frequently asked questions
Who runs Northbrook?
Northbrook (PWSID IL0312070) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Northbrook serve?
Northbrook reports serving 34,407 people through 12,740 service connections in Cook County, Illinois.
Where does Northbrook get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Northbrook have any drinking water violations?
EPA's records list 5 violations for this system; 1 is health-based, and the most recent began in July 2023. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Northbrook's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. EPA's records list 5 violations for this system; 1 is health-based, and the most recent began in July 2023. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Northbrook's water quality report?
As a community water system, Northbrook must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Cook County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Chicago | Cook | 2,721,308 | Community | Surface water |
| Cicero | Cook | 83,000 | Community | Purchased surface water |
| Schaumburg | Cook | 75,750 | Community | Purchased surface water |
| Evanston | Cook | 74,486 | Community | Surface water |
| Arlington Heights | Cook | 73,320 | Community | Purchased surface water |
| Palatine | Cook | 70,875 | Community | Purchased surface water |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Northbrook, PWSID IL0312070, Illinois”, https://aquacensus.com/water-systems/illinois/northbrook-il0312070 (data as of October 1, 2026).