Is Colorado Tap Water Safe to Drink?
Water quality data for 23 cities across Colorado. Find your city below.
Water quality in Colorado varies significantly from city to city. Across 23 cities we track, hardness ranges from 40 PPM in Boulder North to 210 PPM in Parker, with a statewide average of 99 PPM. 6 of 23 cities have hard water above 120 PPM where a water softener provides measurable benefits.
3 Colorado cities have forever chemicals (PFAS) above the EPA's 2024 limit of 4 parts per trillion: Parker (35.35 ppt), Brighton (43.95 ppt), Thornton (48.77 ppt). A reverse osmosis system or NSF P473-certified filter can reduce PFAS to safe levels.
Complete Colorado Guide
Statewide water quality overview, costs, and treatment recommendations.
Well Water in Colorado
Testing, treatment, and common issues for private wells.
Hardest Water Rankings
Colorado cities ranked by water hardness level.
City Treatment Guides
Sized recommendations based on each city's specific water data.
City Comparisons
Parker vs Boulder North
Side-by-side water quality comparison.
Parker vs Castle Rock
Side-by-side water quality comparison.
Castle Rock vs Brighton
Side-by-side water quality comparison.
More for Colorado
Moving to DenverColorado Cities by Water Hardness
| City | Hardness (PPM) | Level | PFAS (ppt) | Source |
|---|---|---|---|---|
| Parker | 210 | Very Hard | 35.35 | Denver Basin aquifer |
| Castle Rock | 200 | Very Hard | 8.95 | Denver Basin aquifer (deep wells) |
| Brighton | 160 | Hard | 43.95 | South Platte River & alluvial wells |
| Greeley | 152 | Hard | 0 | Cache la Poudre River, local wells |
| Lafayette | 150 | Hard | 0 | Colorado-Big Thompson Project |
| Aurora East | 120 | Hard | 23.9 | South Platte River + Prairie Waters |
| Fort Collins | 105 | Moderately Hard | 0 | Cache la Poudre River, Horsetooth Reserv… |
| Colorado Springs | 101 | Moderately Hard | 0 | Mountain watersheds, groundwater |
| Denver | 90 | Moderately Hard | 0 | South Platte River + reservoirs |
| Fort Collins South | 90 | Moderately Hard | 0 | Horsetooth Reservoir + Poudre River |
| Arvada | 81 | Moderately Hard | 0 | Ralston Reservoir, Clear Creek |
| Thornton | 78 | Moderately Hard | 48.77 | Thornton reservoirs, Standley Lake |
| Boulder | 77 | Moderately Hard | 0 | North Boulder Creek, Barker Reservoir |
| Centennial | 75 | Moderately Hard | 0 | South Platte River & Cherry Creek |
| Aurora | 73 | Moderately Hard | 23.9 | South Platte, Arkansas, Homestake |
| Lakewood | 73 | Moderately Hard | 0 | Denver Water system |
| Pueblo | 72 | Moderately Hard | 0 | Arkansas River, Pueblo Reservoir |
| Loveland | 72 | Moderately Hard | 0 | Big Thompson River |
| Broomfield | 70 | Moderately Hard | 0 | South Platte & Boulder Creek |
| Longmont | 68 | Moderately Hard | 0 | Ralph Price Reservoir & local wells |
| Westminster | 66 | Moderately Hard | 0 | Standley Lake, Clear Creek |
| Durango | 45 | Slightly Hard | 0 | Florida River & Animas River |
| Boulder North | 40 | Slightly Hard | 0 | Barker Reservoir + Silver Lake |