Public water system · IL0312100
ActiveNorthfield
At a glance
Northfield (PWSID IL0312100) is an active community water system in Cook County, Illinois. It reports serving 5,470 people through 2,125 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in January 2026.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
5,470
Service connections
2,125
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Northfield compare with other water systems in Cook County?
By EPA's size categories, Northfield is a medium system (3,301 to 10,000 people). Cook County has 251 active public water systems. Its population served is well below the county average of 20,993 people per system, and accounts for 0.1% 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 Northfield is about 18% below 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. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 619 Illinois systems (16%) list purchased surface water as their primary source.
Who owns and regulates Northfield?
EPA lists Northfield 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 Northfield have drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in January 2026. The violations listed here began between December 1992 and January 2026. By type: 1 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 1 as unaddressed and 1 as resolved. Unaddressed means the violation is not resolved or archived and is not yet covered by formal enforcement. 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.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2026-01-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Unaddressed |
| 1992-12-07 | Required treatment not metOCCT/SOWT Study/Recommendation · code 57 | Lead and Copper Rulecode 5000 | Yes | Resolved |
All 2 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.
Northfield: frequently asked questions
Who runs Northfield?
Northfield (PWSID IL0312100) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Northfield serve?
Northfield reports serving 5,470 people through 2,125 service connections in Cook County, Illinois.
Where does Northfield get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Northfield have any drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in January 2026. 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 Northfield'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 2 violations for this system; 1 is health-based, and the most recent began in January 2026. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Northfield's water quality report?
As a community water system, Northfield 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, “Northfield, PWSID IL0312100, Illinois”, https://aquacensus.com/water-systems/illinois/northfield-il0312100 (data as of October 1, 2026).