Colorado Water Quality Report
Tap water quality data for 14 cities in Colorado, updated 2026.
US average: 100 ppm
4 of 14 cities violation-free
14 cities tested
14 water systems tracked
Cleanest Tap Water in Colorado
Cities with the fewest water quality issues
Aurora City of
487K served
Pueblo Board of Ww
114K served
Highlands Ranch Wsd
103K served
Longmont City of
103K served
Boulder City of
166K served
Greeley City of
132K served
Broomfield
106K served
Castle Rock Town of
107K served
Denver
1.3M served
Colorado Springs
469K served
Most Water Quality Issues in Colorado
Cities with the most violations and concerns
Arvada City of
147K served
Thornton City of
226K served
Westminster City of
202K served
Denver
1.3M served
Colorado Springs
469K served
Ft Collins City of
180K served
Castle Rock Town of
107K served
Boulder City of
166K served
Greeley City of
132K served
Broomfield
106K served
Water Hardness Across Colorado
Not sure what your hardness means? Use our Water Hardness Calculator or find the best hardness test kits.
Colorado Tap Water: What You Need to Know
Colorado has 14 tracked water utilities serving approximately 3.8M residents. The average water hardness is 223 ppm (13 GPG), classified as Very Hard — above the national average of 100 ppm. Hardness ranges from 22.7 ppm in Ft Collins City of to 431 ppm in Greeley City of.
In the past 3 years, 10 of 14 cities in Colorado have recorded water quality violations, totaling 65 violations (0 health-based). All 14 tested cities have lead levels below the EPA action level of 15 ppb.
With very hard water on average, many Colorado residents may notice mineral buildup on fixtures, dry skin, or stiff-feeling hair. A shower filter for hard water can help reduce chlorine exposure, while a water softener addresses the mineral buildup directly.
Frequently Asked Questions About Colorado Water
Is tap water safe to drink in Colorado?
Most tap water in Colorado meets EPA standards, but 10 cities have recorded violations in the past 3 years (0 health-based). We recommend checking your specific city's report on TapWater.org and considering a home water test.
How hard is the water in Colorado?
Colorado's average water hardness is 223 ppm (13 GPG), classified as Very Hard. This is above the national average of 100 ppm. Hardness varies significantly by city — use our Water Hardness Calculator to check your specific area.
Which city in Colorado has the cleanest tap water?
Based on EPA violation data, lead testing, and water quality metrics, Aurora City of ranks as having the cleanest tap water in Colorado. It has zero violations in the past 3 years and lead levels well below the EPA action level.
Which city in Colorado has the most water quality issues?
Arvada City of currently has the most water quality concerns in Colorado, with 14 violations in the past 3 years. Residents should check their city's detailed water quality report and consider using a certified water filter.
Where does Colorado get its water from?
The majority of Colorado's water systems (100%) use surface water as their primary source. Surface water comes from rivers, lakes, and reservoirs. Each city's specific source can vary — check individual city reports for details.
All 14 Cities
Sorted by population served
Denver
Utility serves 1.3M
Aurora City of
Utility serves 487K
Colorado Springs
Utility serves 469K
Thornton City of
Utility serves 226K
Westminster City of
Utility serves 202K
Ft Collins City of
Utility serves 180K
Boulder City of
Utility serves 166K
Arvada City of
Utility serves 147K
Greeley City of
Utility serves 132K
Pueblo Board of Ww
Utility serves 114K
Castle Rock Town of
Utility serves 107K
Broomfield
Utility serves 106K
Highlands Ranch Wsd
Utility serves 103K
Longmont City of
Utility serves 103K