How hard is the water in Custer County, CO?

6.3 grains per gallon

Optional: a softener helps, but plenty of homes skip it.

The median hardness measured in Custer County, CO is 108 mg/L as calcium carbonate, which is 6.3 gpg. That is moderately hard on the USGS scale. It comes from 9 samples at 9 sites between 1993 and 2025, drawn from groundwater wells, which is what most taps and private wells in the county draw on.

How much it varies here

Half the sites came in between 5.3 and 8.8 gpg. That spread crosses a decision line, so some homes here land on a different answer. A $10 test strip on your own tap settles it. Confidence in the county figure: medium (how it is measured).

What to do next

At 6.3 gpg this is your call. Look for white film on glasses and crust on the shower head: if you see little of either, you can live without one. If you do want one, a 24,000-grain unit is enough, so ask for that size rather than a bigger one. Because Custer County straddles a decision line, check your own tap with a $10 test strip before you spend anything.

More on when a softener is not worth it.

From 5.1 to 13.6 gpg

The softest single sample on record in Custer County was 87.3 mg/L and the hardest 233 mg/L, a 3-fold gap. The top quarter of sites read above 8.8 gpg and the bottom quarter below 5.3 gpg.

Wells 6.3 gpg, rivers and lakes 8.2 gpg

9 groundwater samples from 9 wells put the median at 108 mg/L. 396 surface samples from 44 sites put it at 140 mg/L. In Custer County the rivers and lakes come out 1.9 gpg harder. Here the surface water reads harder than the wells, which often points to streams fed by limestone springs or irrigation return flow. The two sources are close, so the county figure should hold whichever one your tap is on.

What a softener would cost to run

For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 138 lb of salt a year (4 bags of 40 lb, about $25), and roughly 2,346 gallons of regeneration water. Installed, most units run $1,000 to $4,500; spread over 15 years with salt, that is about $125 a year.

Sizing at 6.3 gpg

Custer County against the rest of Colorado

Among the 63 Colorado counties with data, Custer County is number 50 of 63 counting from the hardest. Across the whole country it is harder than 36% of counties.

Softest in Colorado: Larimer County at 0.4 gpg. Hardest: Mesa County at 143.7 gpg. Closest to Custer County: Gilpin County (6.3), Douglas County (6.5), Dolores County (6.7).