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All 35 cities ranked by water quality score
How Colorado's 35 cities are distributed by water quality grade
20 out of 35 cities meet or exceed a B grade for water quality
Sorted by water quality score from best to worst. Click any city for a detailed water quality report.
| Rank | City | Score | Grade |
|---|---|---|---|
| 1 | Longmont | 96/100 | A+ |
| 2 | Steamboat Springs | 95/100 | A+ |
| 3 | Boulder | 94/100 | A |
| #4 | Broomfield | 93/100 | A |
| #5 | Erie | 93/100 | A |
| #6 | Northglenn | 93/100 | A |
| #7 | Greeley | 92/100 | A |
| #8 | Grand Junction | 90/100 | A |
| #9 | Centennial | 88/100 | A- |
| #10 | Vail | 87/100 | A- |
| #11 | Fort Collins | 86/100 | A- |
| #12 | Lakewood | 84/100 | B+ |
| #13 | Brighton | 83/100 | B+ |
| #14 | Colorado Springs | 83/100 | B+ |
| #15 | Montrose | 82/100 | B+ |
| #16 | Commerce City | 81/100 | B+ |
| #17 | Fort Morgan | 81/100 | B+ |
| #18 | Evans | 80/100 | B+ |
| #19 | Littleton | 80/100 | B+ |
| #20 | Pueblo | 77/100 | B |
| #21 | Denver | 74/100 | B- |
| #22 | Englewood | 71/100 | B- |
| #23 | Thornton | 71/100 | B- |
| #24 | Aurora | 70/100 | B- |
| #25 | Fountain | 68/100 | C+ |
| #26 | Loveland | 68/100 | C+ |
| #27 | Westminster | 68/100 | C+ |
| #28 | Castle Rock | 65/100 | C+ |
| #29 | Lafayette | 65/100 | C+ |
| #30 | Golden | 59/100 | C- |
| #31 | Parker | 53/100 | D |
| #32 | Durango | 51/100 | D |
| #33 | Arvada | 49/100 | F |
| #34 | Wheat Ridge | 49/100 | F |
| #35 | Windsor | 45/100 | F |
The best water quality in Colorado is found in Longmont with a score of 96/100 and a grade of A+. This puts Longmont among the top-performing cities in the country for drinking water safety.
The most concerning water quality is in Windsor scoring 45/100 with a grade of F. Residents may want to consider home water testing and filtration options.
5 cities with D or F grades:
The statewide average score is 76/100, which is 4 points above the national average of 72/100. Over half (60%) of Colorado cities score above the national average, though some areas face challenges.
Longmont has the best water quality in Colorado with a score of 96/100 and a grade of A+. This score is based on contaminant levels, EPA compliance history, and infrastructure quality. Longmont ranks among the top cities nationally for water quality.
Water quality varies across Colorado. The state average score is 76/100. 57% of Colorado cities have good water quality (grade B or better). However, 5 cities have water quality concerns with a grade of D or F. Residents in those areas should consider water testing and filtration. Always check your specific city's water quality report for the most accurate local information.
Of the 35 cities tracked in Colorado, 5 cities have a D or F grade, indicating significant water quality concerns. An additional 6 cities fall in the C range, suggesting moderate issues. 21 out of 35 cities (60%) score above the national average of 72/100. Residents concerned about their water quality can check their city's detailed report for specific contaminant information.
State water quality summary and key statistics
Top 20 cities with the cleanest water
Top-ranked cities nationwide
Cities with the most concerning water
Compare water quality across all 50 states
Side-by-side water quality comparison