How hard is the water in Ada County, ID?
7.4 grains per gallon
A softener is worth it here.
The median hardness measured in Ada County, ID is 128 mg/L as calcium carbonate, which is 7.4 gpg. That is hard on the USGS scale. It comes from 831 samples at 280 sites between 1990 and 2019, 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 4.4 and 11.6 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 7.4 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 Ada 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 0.0 to 38.2 gpg
The softest single sample on record in Ada County was 0.3 mg/L and the hardest 654 mg/L, a 2,180-fold gap. The top quarter of sites read above 11.6 gpg and the bottom quarter below 4.4 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 7.4 gpg, rivers and lakes 2.5 gpg
831 groundwater samples from 280 wells put the median at 127.5 mg/L. 63 surface samples from 7 sites put it at 42.8 mg/L. In Ada County the wells come out 4.9 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 163 lb of salt a year (5 bags of 40 lb, about $29), 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 $129 a year.
Sizing at 7.4 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 444 | 24,000 | 54 lb |
| 2 | 888 | 24,000 | 108 lb |
| 4 | 1,776 | 24,000 | 216 lb |
| 6 | 2,664 | 24,000 | 324 lb |
Ada County against the rest of Idaho
Among the 44 Idaho counties with data, Ada County is number 28 of 44 counting from the hardest. Across the whole country it is harder than 41% of counties.
Softest in Idaho: Valley County at 1.3 gpg. Hardest: Caribou County at 23 gpg. Closest to Ada County: Washington County (7.6), Boundary County (7.1), Lewis County (7.9).