Loading water data...
Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality scores for 35 cities in Colorado
Across the 35 Colorado water systems we track, the average water quality score is 76/100 — 4 points above the U.S. national average of 72/100. 60% of Colorado cities (21 of 35) score above that national benchmark, and 11 earn a Grade A for clean, low-contaminant tap water.
The contaminants most commonly flagged in Colorado water systems are heavy metals (legacy mine drainage), uranium and radium (naturally occurring) and selenium (western slope geology). See the full breakdown in our Colorado water quality rankings or compare against the cities with the best water quality in America.
See the top 20 cities with the cleanest, safest drinking water
Complete water quality rankings for every city in Colorado
98,885 residents
13,932 residents
105,673 residents
74,112 residents
31,859 residents
38,697 residents
108,649 residents
65,560 residents
108,418 residents
5,305 residents
169,810 residents
155,984 residents
41,886 residents
478,961 residents
20,291 residents
62,418 residents
11,555 residents
22,825 residents
46,729 residents
111,876 residents
715,522 residents
34,840 residents
141,867 residents
386,261 residents
31,983 residents
82,329 residents
116,317 residents
73,158 residents
31,962 residents
21,254 residents
58,512 residents
19,399 residents
124,402 residents
32,133 residents
32,551 residents
Colorado's water originates high in the Rocky Mountains, giving much of the state clean, snowmelt-fed surface water. The most distinctive water quality issues stem from the state's legacy of hard-rock mining, which left abandoned mines that can leach heavy metals into headwater streams, and from naturally occurring radionuclides and selenium in some groundwater basins.
Based on our analysis of 35 cities in Colorado, the average water quality score is 76/100. 11 cities have water quality scores below 70, indicating potential concerns that residents should be aware of. The highest-rated city is Windsor with a score of 45/100, while Longmont has the most room for improvement at 96/100.
11 of the 35 Colorado cities we analyzed score below 70/100. If your city is one of them, a certified filter matched to your local contaminants is the fastest way to reduce exposure. For lead and PFAS, look for an NSF 53 certified filter or a reverse osmosis system.
We may earn a commission when you purchase through our links, at no extra cost to you.
Colorado is a headwaters state, with the Colorado, Arkansas, Rio Grande, and South Platte rivers all originating within its borders. Front Range cities such as Denver, Colorado Springs, and Aurora rely on mountain reservoirs and transbasin diversions, while the Eastern Plains and San Luis Valley depend on groundwater aquifers.
These contaminants have been detected in various Colorado water systems
The Colorado Department of Public Health and Environment (CDPHE) administers drinking water programs and oversees cleanup of mine-impacted watersheds, including federal Superfund sites. Colorado has been active on PFAS sampling, particularly near military bases and the Colorado Springs area.
Communities near historic mining districts should be aware of heavy-metal contamination in source water, though treatment generally removes it before delivery. Naturally occurring uranium and radium affect some groundwater systems on the plains. PFAS has been detected near Peterson Space Force Base and parts of the Fountain Valley.
Colorado residents on private wells should test for uranium, radium, nitrate, and metals depending on their location. Reverse osmosis effectively removes uranium, radium, selenium, and most metals. Front Range residents on municipal supplies enjoy generally excellent water but should address lead plumbing in older homes.
Water quality in Colorado varies by location. Our analysis shows an average score of 76/100 across 35 cities, with 11 cities showing potential concerns. We recommend checking your specific city's water quality report and considering filtration if needed.
The most common water quality concerns in Colorado include heavy metals (legacy mine drainage), uranium and radium (naturally occurring), selenium (western slope geology). These contaminants can come from natural sources, industrial activities, or aging infrastructure. Review your city's specific report to see which contaminants affect your area.
Whether you need a water filter depends on your specific location and health concerns. With 11 cities in Colorado showing elevated contaminant levels, residents in those areas may benefit from filtration. Look for filters certified by NSF/ANSI to remove the specific contaminants found in your area.
Public water systems in Colorado are required to provide annual Consumer Confidence Reports (CCRs) to residents. You can usually find your report on your water utility's website, request it by phone, or access it through the EPA's database. Our city-level reports above summarize key information from these official sources.
Lead can be present in Colorado water, primarily from older plumbing infrastructure. Homes built before 1986 may have lead pipes or lead solder. While water treatment plants remove lead, it can leach into water from service lines and home plumbing. Check your city's specific report for lead testing data, and consider having your tap water tested if you live in an older home.
PFAS ("forever chemicals") have been detected in water systems across the United States, including in Colorado. These chemicals are associated with industrial sites, military bases, and firefighting foam use. The EPA has set new PFAS limits effective 2024. Check individual Colorado city reports for PFAS testing results in your area.
Based on our analysis, Windsor has the highest water quality score in Colorado at 45/100 (Grade F). However, "best" depends on your specific health concerns. View our Best Water Quality in Colorado page for a complete ranking.
Public water systems in Colorado are required by the EPA to test water regularly. Testing frequency depends on the contaminant: bacteria testing occurs daily to weekly, while chemical contaminants may be tested quarterly or annually. Results are published in annual Consumer Confidence Reports. Our site aggregates this data from EPA's SDWIS database.
Compare water quality across counties and find data for your area