Colorado Tap Water Quality Rankings 2026: 17th in Nation | WaterQ

Colorado ranks 17th in our 2026 national tap water quality analysis. The state benefits from some of the cleanest source water in the country — high-elevation snowmelt feeding well-managed reservoirs — but more than a century of hardrock mining in the Rocky Mountains has left a lasting legacy in certain watersheds that requires ongoing, active water treatment to this day.

Key Findings for Colorado

Reviewing EPA SDWIS data for 2026, three themes define Colorado's water quality landscape:

• Legacy Mining Impacts: Historic hardrock mining across Colorado's mountains left behind abandoned mines that can leach heavy metals like cadmium, lead, and zinc into nearby streams. Sites such as the area around the 2015 Gold King Mine release now have permanent water treatment facilities that continuously treat acid mine drainage before it reaches downstream water sources.
• High-Quality Mountain Source Water: Denver, Colorado Springs, and most Front Range utilities draw from protected high-elevation reservoirs fed by snowmelt, providing a strong starting point for treatment and contributing to generally low violation rates.
• PFAS Near Military Airfields: Areas near current and former military installations, including parts of the Colorado Springs region, have been associated with PFAS detections in groundwater linked to historical firefighting foam use.

Most Common Contaminants in Colorado

Here's what Colorado residents should know about the contaminants most relevant to their water:

1. Heavy Metals (Legacy Mining)

In mountain watersheds with a history of hardrock mining, abandoned mine drainage can contain elevated cadmium, lead, manganese, and zinc. Active treatment facilities at known sites continuously remove these metals, and municipal water systems downstream are monitored to ensure compliance with federal standards.

2. PFAS ("Forever Chemicals")

PFAS contamination near military airfields, particularly in parts of the Colorado Springs area, has prompted groundwater monitoring and, in some cases, treatment or alternative source development for affected water providers.

3. Radionuclides

Some groundwater systems on Colorado's eastern plains have naturally occurring radionuclides such as uranium and radium, tied to local geology. Affected systems use ion-exchange or reverse osmosis treatment to meet federal standards.

Colorado's Best and Worst Cities for Water Quality

Explore the full breakdown on our Colorado water systems page.

Top Performers: Front Range utilities including Denver Water, drawing from protected mountain reservoirs with modern treatment, generally maintain strong compliance records.

Areas to Watch: Communities near historic mining districts rely on continuous active treatment of mine drainage, areas near military airfields remain under PFAS monitoring, and some eastern plains groundwater systems manage naturally occurring radionuclides.

What Colorado Residents Should Do

Given Colorado's 17th place ranking, here's what matters most for residents:

1. Search Your System's Record: Use the WaterQ search tool to view your water system's violation history and recent contaminant levels.
2. Check PFAS Status If Near a Military Site: Residents near current or former military airfields should check their utility's PFAS monitoring results.
3. Test Private Wells: Mountain residents on private wells near historic mining areas, and eastern plains residents on private wells, should test for relevant local contaminants including metals and radionuclides.
4. Use Appropriate Filtration: Reverse osmosis is effective for both heavy metals and radionuclides, while activated carbon and ion-exchange systems address PFAS and specific metals respectively.

Source: Colorado Department of Public Health and Environment Water Quality Control Division, EPA SDWIS 2026 Compliance Data, and WaterQ National Database. For more information on our ranking process, visit our state rankings page.