How hard is the water in Latah County, ID?
6.7 grains per gallon
Optional: a softener helps, but plenty of homes skip it.
The median hardness measured in Latah County, ID is 116 mg/L as calcium carbonate, which is 6.7 gpg. That is moderately hard on the USGS scale. It comes from 188 samples at 48 sites between 1990 and 2016, 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 5 and 8.1 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 6.7 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 Latah 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 1.1 to 15.7 gpg
The softest single sample on record in Latah County was 19 mg/L and the hardest 269 mg/L, a 14-fold gap. The top quarter of sites read above 8.1 gpg and the bottom quarter below 5 gpg.
Wells 6.7 gpg, rivers and lakes 1.5 gpg
188 groundwater samples from 48 wells put the median at 115.5 mg/L. 25 surface samples from 5 sites put it at 26.5 mg/L. In Latah County the wells come out 5.2 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. 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 147 lb of salt a year (4 bags of 40 lb, about $27), 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 $127 a year.
Sizing at 6.7 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 402 | 24,000 | 49 lb |
| 2 | 804 | 24,000 | 98 lb |
| 4 | 1,608 | 24,000 | 196 lb |
| 6 | 2,412 | 24,000 | 293 lb |
Latah County against the rest of Idaho
Among the 44 Idaho counties with data, Latah County is number 30 of 44 counting from the hardest. Across the whole country it is harder than 38% of counties.
Softest in Idaho: Valley County at 1.3 gpg. Hardest: Caribou County at 23 gpg. Closest to Latah County: Nez Perce County (6.5), Boundary County (7.1), Clearwater County (6.3).