How hard is the water in Washington County, ID?
7.6 grains per gallon
A softener is worth it here.
The median hardness measured in Washington County, ID is 131 mg/L as calcium carbonate, which is 7.6 gpg. That is hard on the USGS scale. It comes from 154 samples at 44 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 3.7 and 17.4 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 7.6 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 Washington 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 1.4 to 44.0 gpg
The softest single sample on record in Washington County was 24.6 mg/L and the hardest 754 mg/L, a 31-fold gap. The top quarter of sites read above 17.4 gpg and the bottom quarter below 3.7 gpg. So even here some sites draw water soft enough to need nothing at all.
Wells 7.6 gpg, rivers and lakes 5.7 gpg
154 groundwater samples from 44 wells put the median at 130.5 mg/L. 28 surface samples from 2 sites put it at 97.6 mg/L. In Washington County the wells come out 1.9 gpg harder. Groundwater sits in contact with rock for years and picks up calcium and magnesium as it goes, so wells usually read harder. 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 166 lb of salt a year (5 bags of 40 lb, about $30), 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 $130 a year.
Sizing at 7.6 gpg
| People | Grains a day | Unit | Salt a year |
|---|---|---|---|
| 1 | 456 | 24,000 | 55 lb |
| 2 | 912 | 24,000 | 111 lb |
| 4 | 1,824 | 24,000 | 222 lb |
| 6 | 2,736 | 24,000 | 333 lb |
Washington County against the rest of Idaho
Among the 44 Idaho counties with data, Washington County is number 27 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 Washington County: Ada County (7.4), Lewis County (7.9), Boundary County (7.1).