Denver Metro Water Hardness Map & Data by City
Water hardness varies significantly across the Denver Metro area depending on the water source. While some cities enjoy moderately soft water from mountain snowmelt, others relying on groundwater or mixed sources experience much harder water. This page provides a visual comparison of water hardness (measured in Grains Per Gallon, or GPG) across 15 local cities.
Water Hardness by City (GPG)
Hardness Scale Legend
Soft (0–3.5 GPG)
Minimal scaling.
Moderate (3.5–7 GPG)
Noticeable spotting.
Hard (7–10.5 GPG)
Scale buildup occurs. Softener recommended.
Very Hard (10.5+ GPG)
Severe scaling. Softener required.
Why the variation?
Cities closer to the foothills (like Boulder) often draw directly from surface water sources that haven't had time to absorb minerals. Cities further east or those relying on well water (like Brighton or Castle Rock) draw from sources that have dissolved more calcium and magnesium.
Detailed City Data
Click any column header to sort the table.
| City ↕ | GPG ↓ | Classification ↕ | Primary Water Source |
|---|---|---|---|
| Brighton | 10.2 | Hard | South Platte Alluvial Aquifer |
| Castle Rock | 9.5 | Hard | Denver Basin Aquifers |
| Parker | 9.1 | Hard | Cherry Creek & Wells |
| Commerce City | 8.8 | Hard | South Platte Water |
| Highlands Ranch | 8.5 | Hard | Centennial Water |
| Centennial | 8.3 | Hard | Denver & Aurora Water |
| Aurora | 8.2 | Hard | South Platte, Colorado & Arkansas |
| Englewood | 8 | Hard | South Platte River |
| Littleton | 7.9 | Hard | Denver Water |
| Denver | 7.8 | Hard | South Platte & Colorado Rivers |
| Lakewood | 7.6 | Hard | Denver Water |
| Arvada | 7.5 | Hard | Denver Water & Clear Creek |
| Westminster | 7.4 | Hard | Clear Creek & Standley Lake |
| Longmont | 6.8 | Moderate | St. Vrain Creek & Colorado River |
| Boulder | 4.2 | Moderate | Arapahoe Glacier & Barker Res |