States → Wisconsin
State profile · EPA SDWIS + UCMR5
Wisconsin Drinking Water Quality
10,988 public water systems serve 5,131,439 people across Wisconsin, with every Safe Drinking Water Act violation and UCMR5 PFAS result on record.
- 10,988
- Water systems
- 285,161
- Total violations
- 72.1%
- Systems w/ a violation
- 38.6%
- PFAS detection rate
The verdict
Across Wisconsin, 7,923 of 10,988 water systems (72.1%) carry at least one EPA violation, and 78 of 202 UCMR5-tested systems show PFAS.
- 285,161
- Total EPA violations on record
- 21%
- Health-based (MCL / treatment)
- 72.1%
- Systems with ≥1 violation
- 38.6%
- UCMR5 PFAS detection rate
Water Systems
10,988
Total Violations
285,161
Violation Rate
72.1%
PFAS Detection
38.6%
78 of 202 tested
Violation Composition
How Wisconsin's 285,161 violations break down by type, per EPA SDWIS classification.
Health-based (58,688) Monitoring/Reporting (226,473)
| Metric | Value | Share |
|---|---|---|
| Public water systems | 10,988 | - |
| Population served | 5,131,439 | - |
| Total violations | 285,161 | 100% |
| Health-based violations | 58,688 | 20.6% |
| Systems with violations | 7,923 | 72.1% |
| PFAS detection rate | 78 of 202 | 38.6% |
Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement. Monitoring/reporting violations indicate procedural issues (missed tests, late reports) - not necessarily a contamination event.
Largest Water Systems
Milwaukee Waterworks
Milwaukee, WI · 626,000 served
Madison Water Utility
Madison, WI · 272,000 served
Green Bay Waterworks
Green Bay, WI · 107,369 served
Racine Waterworks
Racine, WI · 105,100 served
Kenosha Water Utility
Kenosha, WI · 99,218 served
Appleton Waterworks
Appleton, WI · 74,511 served
Waukesha Water Utility
Waukesha, WI · 70,718 served
Eau Claire Waterworks
Eau Claire, WI · 70,587 served
Janesville Water Utility
Janesville, WI · 64,415 served
West Allis Waterworks
West Allis, WI · 63,240 served
Oshkosh Waterworks
Oshkosh, WI · 63,000 served
La Crosse Waterworks
La Crosse, WI · 53,000 served
Sheboygan Water Utilities
Sheboygan, WI · 49,931 served
Wauwatosa Waterworks
Wauwatosa, WI · 49,064 served
Fond Du Lac Waterworks
Fond Du Lac, WI · 44,303 served
Wausau Waterworks
Wausau, WI · 39,994 served
Beloit City Of
Beloit, WI · 36,677 served
North Shore Water Commission
Milwaukee, WI · 35,598 served
Manitowoc Waterworks
Manitowoc, WI · 34,500 served
Sun Prairie Utilities
Sun Prairie, WI · 33,966 served
Most Violations
#1 Waukesha Water Utility Waukesha
2,969 #2 52nd Ave Water Group Kenosha
1,760 #3 337-9 Holy Hill Apartments LLC Libertyville
1,498 #4 Sussex Village Hall & Water Utility Sussex
1,254 #5 Maple Ridge Estates Stevens Point
1,161 #6 Wilmot Union High School Wilmot
1,121 #7 Embarrass Waterworks Embarrass
957 #8 Amery Free Lutheran Church Amery
896 #9 Emr LLC Dba 5 Corners Truck & Auto Cedarburg
886 #10 Ashland Ford Chrysler Ashland
866 #11 Willow Lane Estates Stevens Point
857 #12 Shady Oaks MHP Spring Valley
825 #13 American Champion Aircraft Rochester
800 #14 St Johns Lutheran School Newburg
767 #15 Montreal Waterworks Montreal
766 Counties in Wisconsin
Milwaukee
85 systems · 953,104 served
· 2,602 violations
Dane
301 systems · 517,785 served
· 7,065 violations
Waukesha
590 systems · 322,690 served
· 24,998 violations
Brown
149 systems · 246,872 served
· 2,891 violations
Outagamie
107 systems · 179,535 served
· 1,999 violations
Racine
195 systems · 179,476 served
· 10,597 violations
Winnebago
152 systems · 151,482 served
· 1,690 violations
Rock
156 systems · 148,582 served
· 3,788 violations
Kenosha
227 systems · 137,280 served
· 15,435 violations
Washington
268 systems · 131,895 served
· 7,862 violations
Sheboygan
215 systems · 119,678 served
· 5,035 violations
Marathon
195 systems · 103,485 served
· 5,385 violations
La Crosse
125 systems · 98,968 served
· 3,426 violations
Walworth
252 systems · 95,076 served
· 10,507 violations
Eau Claire
111 systems · 92,606 served
· 2,862 violations
Ozaukee
252 systems · 91,746 served
· 13,722 violations
Jefferson
194 systems · 90,591 served
· 2,740 violations
Fond du Lac
211 systems · 86,612 served
· 5,061 violations
Dodge
180 systems · 73,540 served
· 5,065 violations
Sauk
199 systems · 68,432 served
· 4,499 violations
Columbia
141 systems · 64,692 served
· 3,867 violations
Manitowoc
143 systems · 64,329 served
· 2,305 violations
Wood
148 systems · 58,513 served
· 2,172 violations
St. Croix
164 systems · 56,107 served
· 3,287 violations
Chippewa
219 systems · 52,060 served
· 3,638 violations
Portage
150 systems · 50,413 served
· 2,795 violations
Vilas
466 systems · 42,533 served
· 4,566 violations
Grant
89 systems · 41,605 served
· 3,251 violations
Oneida
346 systems · 40,522 served
· 4,836 violations
Monroe
97 systems · 39,109 served
· 2,390 violations
Showing top 30 of 71 counties.
Drinking Water Guides
Frequently Asked Questions
How many water systems are in Wisconsin? ▼
Wisconsin has 10,988 public water systems serving approximately 5,131,439 people. These include community water systems, non-transient non-community systems, and transient non-community systems regulated under the Safe Drinking Water Act.
How many drinking water violations are in Wisconsin? ▼
Wisconsin has 285,161 total drinking water violations on record, with 58,688 classified as health-based violations. 72.1% of water systems in the state have at least one violation.
Has PFAS been found in Wisconsin drinking water? ▼
Of 202 water systems tested for PFAS in Wisconsin, 78 had PFAS detected, a 38.6% detection rate. PFAS are persistent "forever chemicals" that do not break down in the environment.
What is the violation rate for Wisconsin water systems? ▼
Wisconsin's violation rate is 72.1%. This measures the percentage of public water systems that have at least one recorded violation in the EPA SDWIS database, including both health-based and monitoring/reporting violations.
Where does this Wisconsin water data come from? ▼
All drinking water data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS is the federal database that tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources & Methodology
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.