Public water system · IL1110400
ActiveLake in the Hills
At a glance
Lake in the Hills (PWSID IL1110400) is an active community water system in McHenry County, Illinois. It reports serving 28,661 people through 9,590 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in January 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
28,661
Service connections
9,590
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Lake in the Hills compare with other water systems in McHenry County?
By EPA's size categories, Lake in the Hills is a large system (10,001 to 100,000 people). McHenry County has 192 active public water systems, and Lake in the Hills is the 3rd-largest of them by population served. Its population served is about 22 times the county average of 1,331 people per system, and accounts for 11% of the 255,516 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 Lake in the Hills is about 4.3 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. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 2,808 Illinois systems (73%) list groundwater as their primary source.
Who owns and regulates Lake in the Hills?
EPA lists Lake in the Hills 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. 35 of the 192 active systems in McHenry County (18%) are also owned by a local government.
Does Lake in the Hills have drinking water violations?
Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in January 2025. The violations listed here began between January 1995 and January 2025. By type: 7 monitoring and reporting, 3 contaminant level above the legal limit and 2 public notice, recordkeeping or other. The contaminant or rule involved most often is Total coliform bacteria (TCR) (5 of them). EPA lists 7 as resolved and 5 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 |
|---|---|---|---|---|
| 2025-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Archived |
| 2025-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Archived |
| 2012-08-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2012-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2006-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 2005-09-10 | Public notice, recordkeeping or otherPublic Notification Violation for NPDWR Violation · code 75 | Public Noticecode 7500 | No | Resolved |
| 2005-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 1999-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Bariumcode 1010 | No | Resolved |
| 1999-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitratecode 1040 | No | Resolved |
| 1997-07-01 | Monitoring and reportingMonitoring, Repeat Minor (TCR) · code 26 | Total coliform bacteria (TCR)code 3100 | No | Archived |
| 1997-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Archived |
| 1995-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Archived |
The 12 most recent 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.
Lake in the Hills: frequently asked questions
Who runs Lake in the Hills?
Lake in the Hills (PWSID IL1110400) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Lake in the Hills serve?
Lake in the Hills reports serving 28,661 people through 9,590 service connections in McHenry County, Illinois.
Where does Lake in the Hills get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Lake in the Hills have any drinking water violations?
Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in January 2025. 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 Lake in the Hills' 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. Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in January 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Lake in the Hills' water quality report?
As a community water system, Lake in the Hills 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 McHenry County
Related pages
Working with water-system records? Pro adds alerts, change history and CSV export ($49/mo); Enterprise adds full national files, the API and an MCP server for AI tools.
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, “Lake in the Hills, PWSID IL1110400, Illinois”, https://aquacensus.com/water-systems/illinois/lake-in-the-hills-il1110400 (data as of October 1, 2026).