How hard is the water in Costilla County, CO?

4.9 grains per gallon

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

The median hardness measured in Costilla County, CO is 84 mg/L as calcium carbonate, which is 4.9 gpg. That is moderately hard on the USGS scale. It comes from 552 samples at 52 sites between 1992 and 2025, drawn from every sampling site in the county, wells and surface water together.

How much it varies here

Half the sites came in between 4.1 and 5.7 gpg. The whole middle of that range gives the same answer, so a test of your own tap is unlikely to change it. Confidence in the county figure: high (how it is measured).

What to do next

At 4.9 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.

More on when a softener is not worth it.

From 0.1 to 12.9 gpg

The softest single sample on record in Costilla County was 1 mg/L and the hardest 220 mg/L, a 220-fold gap. The top quarter of sites read above 5.7 gpg and the bottom quarter below 4.1 gpg.

What a softener would cost to run

For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 107 lb of salt a year (3 bags of 40 lb, about $19), 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 $119 a year.

Sizing at 4.9 gpg

Costilla County against the rest of Colorado

Among the 63 Colorado counties with data, Costilla County is number 56 of 63 counting from the hardest. Across the whole country it is harder than 30% of counties.

Softest in Colorado: Larimer County at 0.4 gpg. Hardest: Mesa County at 143.7 gpg. Closest to Costilla County: Prowers County (5.3), Saguache County (4.4), Chaffee County (4.3).