Wisconsin water quality
Wisconsin has 8,749 active public water systems (22,144 on file total), 831 of them graded by TapGraded.
Grade distribution
Biggest water systems
MILWAUKEE WATERWORKS
MILWAUKEE, WI · 626,000 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
WEST ALLIS WATERWORKS
WEST ALLIS, WI · 63,240 served
OSHKOSH WATERWORKS
OSHKOSH, WI · 63,000 served
SHEBOYGAN WATER UTILITIES
SHEBOYGAN, WI · 49,931 served
WAUWATOSA WATERWORKS
Wauwatosa, WI · 49,064 served
NORTH SHORE WATER COMMISSION
MILWAUKEE, WI · 35,598 served
Lowest-graded systems
Active, graded systems serving at least 10,000 people, ordered by lowest Tap Grade first.
BURLINGTON WATERWORKS
BURLINGTON, WI · 11,043 served
MARSHFIELD UTILITIES
MARSHFIELD, WI · 18,815 served
TWO RIVERS WATERWORKS
TWO RIVERS, WI · 11,270 served
HARTFORD WATERWORKS
HARTFORD, WI · 15,805 served
WATERTOWN WATERWORKS
WATERTOWN, WI · 23,945 served
WHITEWATER WATERWORKS
WHITEWATER, WI · 14,000 served
ELKHORN WATERWORKS
ELKHORN, WI · 10,317 served
SUPERIOR WATER LIGHT & POWER COMPANY
SUPERIOR, WI · 26,084 served
HOWARD WATERWORKS
GREEN BAY, WI · 21,133 served
ALLOUEZ WATERWORKS
GREEN BAY, WI · 13,923 served
Cities in Wisconsin
Source: EPA SDWIS/ECHO · Data as of 2026Q2