How hard is the water in Bonner County, ID?
5.8 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Bonner County, ID is 99 mg/L as calcium carbonate, which is 5.8 gpg. That is moderately hard on the USGS scale. It comes from 293 samples at 76 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 3.9 and 8.3 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 5.8 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. Because Bonner County straddles a decision line, check your own tap with a $10 test strip before you spend anything.
More on when a softener is not worth it.
From 0.5 to 42.9 gpg
The softest single sample on record in Bonner County was 8.5 mg/L and the hardest 735 mg/L, an 86-fold gap. The top quarter of sites read above 8.3 gpg and the bottom quarter below 3.9 gpg.
Wells 5.8 gpg, rivers and lakes 4.6 gpg
293 groundwater samples from 76 wells put the median at 99.1 mg/L. 492 surface samples from 13 sites put it at 78.7 mg/L. In Bonner County the wells come out 1.2 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 126 lb of salt a year (4 bags of 40 lb, about $23), 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 $123 a year.
Sizing at 5.8 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 348 | 24,000 | 42 lb |
| 2 | 696 | 24,000 | 85 lb |
| 4 | 1,392 | 24,000 | 169 lb |
| 6 | 2,088 | 24,000 | 254 lb |
Bonner County against the rest of Idaho
Among the 44 Idaho counties with data, Bonner County is number 35 of 44 counting from the hardest. Across the whole country it is harder than 34% of counties.
Softest in Idaho: Valley County at 1.3 gpg. Hardest: Caribou County at 23 gpg. Closest to Bonner County: Kootenai County (5.9), Idaho County (5.5), Fremont County (6).