How hard is the water in San Juan County, CO?
16.2 grains per gallon
A softener will pay its way here.
The median hardness measured in San Juan County, CO is 277 mg/L as calcium carbonate, which is 16.2 gpg. That is very hard on the USGS scale. It comes from 27 samples at 26 sites between 1990 and 2026, 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 10 and 56.1 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 16.2 gpg a softener pays its way here. Before you buy, check the quoted unit's grain capacity against the sizing table below, and ask whether it regenerates on demand, which uses less salt than a timer. Call your utility for its own report if you are on city water. Because San Juan County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on sizing a softener for your household.
From 2.8 to 85.3 gpg
The softest single sample on record in San Juan County was 47.1 mg/L and the hardest 1,460 mg/L, a 31-fold gap. The top quarter of sites read above 56.1 gpg and the bottom quarter below 10 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 16.2 gpg, rivers and lakes 5.3 gpg
27 groundwater samples from 26 wells put the median at 277 mg/L. 3,863 surface samples from 238 sites put it at 90.9 mg/L. In San Juan County the wells come out 10.9 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. A utility here that draws from the river can deliver noticeably different water from a private well next door.
What a softener would cost to run
For a household of 3, a 24,000-grain unit covers a week between regenerations. Expect about 353 lb of salt a year (9 bags of 40 lb, about $64), 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 $164 a year.
Sizing at 16.2 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 972 | 24,000 | 118 lb |
| 2 | 1,944 | 24,000 | 237 lb |
| 4 | 3,888 | 32,000 | 473 lb |
| 6 | 5,832 | 48,000 | 710 lb |
San Juan County against the rest of Colorado
Among the 63 Colorado counties with data, San Juan County is number 21 of 63 counting from the hardest. Across the whole country it is harder than 73% of counties.
Softest in Colorado: Larimer County at 0.4 gpg. Hardest: Mesa County at 143.7 gpg. Closest to San Juan County: Ouray County (15.9), Baca County (15.8), Moffat County (15.8).