Colorado water quality
Colorado has 2,272 active public water systems (4,989 on file total), 1,108 of them graded by TapGraded.
Grade distribution
Biggest water systems
DENVER WATER BOARD
DENVER, CO · 1,287,000 served
AURORA CITY OF
AURORA, CO · 533,407 served
COLORADO SPRINGS UTILITIES
COLORADO SPRINGS, CO · 464,111 served
THORNTON CITY OF
THORNTON, CO · 226,465 served
WESTMINSTER CITY OF
WESTMINSTER, CO · 202,078 served
FT COLLINS CITY OF
FORT COLLINS, CO · 179,901 served
ARVADA CITY OF
ARVADA, CO · 171,610 served
BOULDER CITY OF
BOULDER, CO · 166,080 served
GREELEY CITY OF
GREELEY, CO · 132,310 served
PUEBLO BOARD OF WW
PUEBLO, CO · 114,070 served
Lowest-graded systems
Active, graded systems serving at least 10,000 people, ordered by lowest Tap Grade first.
ENGLEWOOD CITY OF
ENGLEWOOD, CO · 57,332 served
MT WERNER WD
STEAMBOAT SPRINGS, CO · 19,000 served
FT LUPTON CITY OF
FORT LUPTON, CO · 12,099 served
THORNTON CITY OF
THORNTON, CO · 226,465 served
PARKER WSD
PARKER, CO · 75,949 served
WIDEFIELD WSD
COLORADO SPRINGS, CO · 27,640 served
COTTONWOOD WSD
ENGLEWOOD, CO · 10,867 served
BRIGHTON CITY OF
BRIGHTON, CO · 56,304 served
LITTLE THOMPSON WD
BERTHOUD, CO · 25,654 served
BRECKENRIDGE TOWN OF
BRECKENRIDGE, CO · 28,315 served
Cities in Colorado
Source: EPA SDWIS/ECHO · Data as of 2026Q2