Denver water hardness: about 6 grains per gallon
Denver tap water is moderately hard: about 6.1 grains per gallon (105 mg/L) on average. That figure comes from Denver Water's 2026 water quality report (PDF, opens in new tab), which covers 2025. Samples ranged from 55 to 124 mg/L, or about 3.2 to 7.3 grains per gallon.
Denver water hardness
Grains per gallon, from Denver Water's 2026 water quality report. Sacramento river water shown for comparison.
Where does Denver water come from?
Denver Water's report says its sources include the upper South Platte River and the upper Blue River, fed mostly by mountain snowmelt. Snowmelt has not had much time to pick up minerals, so it starts out fairly soft.
Denver Water's hardness page (opens in new tab) says it runs two main collection systems. The southern one is moderately hard and the northern one is somewhat soft. Live in a suburb with its own utility, like Aurora? Check that utility's report for your number.
What this means at home
- Some white scale on faucets and shower heads over time
- Light spotting on dishes
- Residue from cold water humidifiers, which Denver Water itself mentions
- Slow scale buildup inside water heaters
Do you need a water softener in Denver?
Probably not. At about 6 grains per gallon, most Denver Water homes can skip a softener and wipe down fixtures now and then. If you are on the harder southern system, or you are on a private well, test your water first. Your own number is what counts.
Care more about taste? A drinking water filter may suit you better. Read reverse osmosis vs. a water softener.
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Book my free water testCommon questions
Is Denver water hard?
Only moderately. Denver Water's 2026 report shows total hardness in 2025 averaging about 105 mg/L, with a range of 55 to 124 mg/L. That is about 3.2 to 7.3 grains per gallon. Denver Water describes its water as soft to moderately hard.
Why is some Denver water softer than others?
Denver Water says it uses two main collection systems. The southern system is moderately hard and the northern system is somewhat soft, so your number depends on which one serves you.
Do I need a water softener in Denver?
Most Denver Water customers do not need one. At about 6 grains per gallon, scale is mild. A tap test tells you for sure.
Keep reading
DataWater hardness by cityHow hard the tap water is in US cities, from each utility report.
City dataSalt Lake City water hardness: 8 to 12.4 grains per gallon8 to 12.4 grains per gallon. Hard to very hard.
GuideDo I need a water softener with city water?It depends on your city. Here is how to decide.
GuideReverse osmosis vs. water softener: which one do you need?They do different jobs. Here is how to pick.