How hard is the water in Boundary County, ID?
7.1 grains per gallon
A softener is worth it here.
The median hardness measured in Boundary County, ID is 122 mg/L as calcium carbonate, which is 7.1 gpg. That is hard on the USGS scale. It comes from 99 samples at 23 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 2.4 and 14.6 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 7.1 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 Boundary 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 0.5 to 25.9 gpg
The softest single sample on record in Boundary County was 8 mg/L and the hardest 444 mg/L, a 56-fold gap. The top quarter of sites read above 14.6 gpg and the bottom quarter below 2.4 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 7.1 gpg, rivers and lakes 6.4 gpg
99 groundwater samples from 23 wells put the median at 122 mg/L. 52 surface samples from 4 sites put it at 109 mg/L. In Boundary County the wells come out 0.7 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. 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 156 lb of salt a year (4 bags of 40 lb, about $28), 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 $128 a year.
Sizing at 7.1 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 426 | 24,000 | 52 lb |
| 2 | 852 | 24,000 | 104 lb |
| 4 | 1,704 | 24,000 | 207 lb |
| 6 | 2,556 | 24,000 | 311 lb |
Boundary County against the rest of Idaho
Among the 44 Idaho counties with data, Boundary County is number 29 of 44 counting from the hardest. Across the whole country it is harder than 39% of counties.
Softest in Idaho: Valley County at 1.3 gpg. Hardest: Caribou County at 23 gpg. Closest to Boundary County: Latah County (6.7), Ada County (7.4), Washington County (7.6).