How hard is the water in San Juan County, UT?
19.6 grains per gallon
A softener will pay its way here.
The median hardness measured in San Juan County, UT is 335 mg/L as calcium carbonate, which is 19.6 gpg. That is very hard on the USGS scale. It comes from 882 samples at 200 sites between 1990 and 2023, 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 9.4 and 44.2 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: high (how it is measured).
What to do next
At 19.6 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 0.2 to 273.4 gpg
The softest single sample on record in San Juan County was 2.8 mg/L and the hardest 4,680 mg/L, a 1,671-fold gap. The top quarter of sites read above 44.2 gpg and the bottom quarter below 9.4 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 19.6 gpg, rivers and lakes 16.1 gpg
882 groundwater samples from 200 wells put the median at 335 mg/L. 2,783 surface samples from 196 sites put it at 274.8 mg/L. In San Juan County the wells come out 3.5 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 32,000-grain unit covers a week between regenerations. Expect about 427 lb of salt a year (11 bags of 40 lb, about $77), 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 $177 a year.
Sizing at 19.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 1,176 | 24,000 | 143 lb |
| 2 | 2,352 | 24,000 | 286 lb |
| 4 | 4,704 | 40,000 | 572 lb |
| 6 | 7,056 | 64,000 | 858 lb |
San Juan County against the rest of Utah
Among the 29 Utah counties with data, San Juan County is number 7 of 29 counting from the hardest. Across the whole country it is harder than 83% of counties.
Softest in Utah: Davis County at 9 gpg. Hardest: Emery County at 151.3 gpg. Closest to San Juan County: Tooele County (19.5), Carbon County (19), Sanpete County (18.9).