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Wisconsin Water Quality
493
Utilities in database
4.1M
Residents served
38%
On private wells
3
Key contaminants tracked
Drinking Water in Wisconsin
Wisconsin has 493 community water systems serving approximately 4.1 million residents. Primary water sources include groundwater. The most commonly reported contaminants include arsenic, lead, disinfection byproducts. 38% of Wisconsin residents rely on private wells. DNR holds primary enforcement authority under the Safe Drinking Water Act.
Utilities in Wisconsin
Top 20 of 493 by populationMilwaukee Waterworks
WI2410100 · 626,000 served
Madison Water Utility
WI1130224 · 272,000 served
Green Bay Waterworks
WI4050356 · 107,369 served
Racine Waterworks
WI2520062 · 105,100 served
Kenosha Water Utility
WI2300046 · 99,218 served
Appleton Waterworks
WI4450333 · 74,511 served
Waukesha Water Utility
WI2680238 · 70,718 served
Eau Claire Waterworks
WI6180230 · 70,587 served
Janesville Water Utility
WI1540127 · 64,415 served
West Allis Waterworks
WI2410595 · 63,240 served
Oshkosh Waterworks
WI4710457 · 63,000 served
La Crosse Waterworks
WI6320309 · 53,000 served
Sheboygan Water Utilities
WI4600354 · 49,931 served
Wauwatosa Waterworks
WI2410596 · 49,064 served
Fond Du Lac Waterworks
WI4200469 · 44,303 served
Wausau Waterworks
WI7370102 · 39,994 served
City of Beloit
WI1540112 · 36,677 served
North Shore Water Commission
WI2413515 · 35,598 served
Manitowoc Waterworks
WI4360364 · 34,500 served
Sun Prairie Utilities
WI1130258 · 33,966 served
Key Contaminant Concerns in Wisconsin
Lead
Lead is a naturally occurring heavy metal that was widely used in plumbing infrastructure until it was banned for new installations in 1986. An estimated 9.2 million lead service lines still connect homes to public water mains across the United States, along with millions of homes with lead solder in their internal plumbing.
DBPs
When utilities add chlorine to water to kill pathogens, it reacts with dissolved organic matter — leaves, algae, soil — to produce disinfection byproducts (DBPs). Over 600 DBPs have been identified. The EPA regulates two groups: total trihalomethanes (TTHMs, including chloroform) and haloacetic acids (HAA5). DBP levels tend to be highest in surface water systems and in warm months when organic matter is elevated.
Arsenic
Arsenic (As) occurs naturally in rock and soil, dissolving into groundwater through natural weathering processes. Inorganic arsenic — the form found in drinking water — is a known human carcinogen. The western United States has particularly arsenic-rich geological formations, but elevated levels have been found in 48 states. Arsenic is tasteless and odorless.
Wisconsin Water FAQs
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Data source: Utility data from EPA SDWIS. 493 active community water systems ingested. CCR contaminant data ingestion in progress.
Last updated: 2026-04-19