Public water system · IL1870150
ActiveMonmouth
At a glance
Monmouth (PWSID IL1870150) is an active community water system in Warren County, Illinois. It reports serving 8,902 people through 3,800 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, 11 are health-based, and the most recent began in November 2024.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
8,902
Service connections
3,800
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Monmouth compare with other water systems in Warren County?
By EPA's size categories, Monmouth is a medium system (3,301 to 10,000 people). Warren County has 15 active public water systems, and Monmouth is the largest of them by population served. Its population served is about 10 times the county average of 874 people per system, and accounts for 68% of the 13,112 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 Monmouth is about 33% above 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 Monmouth?
EPA lists Monmouth 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. 6 of the 15 active systems in Warren County (40%) are also owned by a local government.
Does Monmouth have drinking water violations?
Of the 12 most recent violations in EPA's records, 11 are health-based, and the most recent began in November 2024. The violations listed here began between January 2004 and November 2024. By type: 11 contaminant level above the legal limit and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Combined Radium (-226 and -228) (8 of them). EPA lists 12 as resolved. 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 |
|---|---|---|---|---|
| 2024-11-28 | Public notice, recordkeeping or otherPublic Notification Violation for NPDWR Violation · code 75 | Public Noticecode 7500 | No | Resolved |
| 2024-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2005-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2005-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Gross alpha (excluding radon and uranium)code 4000 | Yes | Resolved |
| 2005-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2005-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Gross alpha (excluding radon and uranium)code 4000 | Yes | Resolved |
| 2005-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Gross alpha (excluding radon and uranium)code 4000 | Yes | Resolved |
| 2005-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
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.
Monmouth: frequently asked questions
Who runs Monmouth?
Monmouth (PWSID IL1870150) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Monmouth serve?
Monmouth reports serving 8,902 people through 3,800 service connections in Warren County, Illinois.
Where does Monmouth 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 Monmouth have any drinking water violations?
Of the 12 most recent violations in EPA's records, 11 are health-based, and the most recent began in November 2024. 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 Monmouth'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. Of the 12 most recent violations in EPA's records, 11 are health-based, and the most recent began in November 2024. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Monmouth's water quality report?
As a community water system, Monmouth 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 Warren County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Roseville | Warren | 915 | Community | Purchased groundwater |
| Alexis | Warren | 836 | Community | Groundwater |
| Kirkwood | Warren | 714 | Community | Groundwater |
| United School District 304 | Warren | 480 | Non-transient non-community | Groundwater |
| Little Swan Lake Sd | Warren | 438 | Community | Groundwater |
| Little York | Warren | 304 | Community | Purchased groundwater |
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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, “Monmouth, PWSID IL1870150, Illinois”, https://aquacensus.com/water-systems/illinois/monmouth-il1870150 (data as of October 1, 2026).