How hard is the water in Custer County, ID?
8.5 grains per gallon
A softener is worth it here.
The median hardness measured in Custer County, ID is 145 mg/L as calcium carbonate, which is 8.5 gpg. That is hard on the USGS scale. It comes from 165 samples at 44 sites between 1990 and 2018, 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 4.7 and 12.1 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: high (how it is measured).
What to do next
At 8.5 gpg a softener is worth getting, mainly to protect the water heater and cut soap use. Get at least two quotes, ask each installer what grain capacity they are fitting, and check it against the sizing table below. Because Custer 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 0.3 to 34.2 gpg
The softest single sample on record in Custer County was 5.4 mg/L and the hardest 586 mg/L, a 109-fold gap. The top quarter of sites read above 12.1 gpg and the bottom quarter below 4.7 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 8.5 gpg, rivers and lakes 2.2 gpg
165 groundwater samples from 44 wells put the median at 145 mg/L. 164 surface samples from 11 sites put it at 38.5 mg/L. In Custer County the wells come out 6.3 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 185 lb of salt a year (5 bags of 40 lb, about $33), 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 $133 a year.
Sizing at 8.5 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 510 | 24,000 | 62 lb |
| 2 | 1,020 | 24,000 | 124 lb |
| 4 | 2,040 | 24,000 | 248 lb |
| 6 | 3,060 | 24,000 | 372 lb |
Custer County against the rest of Idaho
Among the 44 Idaho counties with data, Custer County is number 23 of 44 counting from the hardest. Across the whole country it is harder than 44% of counties.
Softest in Idaho: Valley County at 1.3 gpg. Hardest: Caribou County at 23 gpg. Closest to Custer County: Clark County (8.5), Lemhi County (8.6), Lincoln County (8.2).