State water index

Idaho water hardness

Search 67 indexed communities and 78 ZIP profiles, then compare the underlying utility, source, distance, and reporting context.

Median regional evidence

165PPM

Hard

Indexed range 22–279 PPM

ZIP profiles: 78
Cities: 67
Matched utilities: 79
Counties: 36

Understanding Idaho

Why local comparisons matter here

Idaho includes mountain watersheds, the volcanic Snake River Plain, agricultural valleys, and northern lake and river systems. Groundwater and surface-water settings vary widely.

In this index, very hard is the largest category, covering 20 of 51 profiles with hardness data. The state median is 165 PPM, but the full indexed range is 22–279 PPM.

State distribution

Hardness across indexed ZIPs

Counts describe published ZIP profiles, not a population-weighted statewide sample.

Soft · 0–60 PPM2

Moderately hard · 61–120 PPM13

Hard · 121–180 PPM16

Very hard · 181+ PPM20

Evidence coverage

What the current records support

Hardness estimate: 65%
Lead 90th percentile: 100%
Copper 90th percentile: 8%

Low-confidence hardness profiles

Research-comparison eligible profiles

Reported source water

Utility source mix

Groundwater: 69
Surface water: 9
Groundwater influenced by surface water: 1

Highest medians

Highest eligible city medians

Lowest medians

Lowest eligible city medians

City directory

Explore Idaho by city

Search by city or county, then sort by name, hardness, or ZIP coverage.

67 cities · 78 ZIP profiles

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County

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67 cities found

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Aberdeen

Bingham County · 1 ZIP

171PPM regional

County	Median	Range	ZIP profiles
Owyhee County	279 PPM	279–279	2
Cassia County	271 PPM	270.5–270.5	1
Minidoka County	254 PPM	254–254	3
Twin Falls County	226 PPM	180–262	5
Power County	223 PPM	223–223	1
Caribou County	210 PPM	210–210	1
Franklin County	203 PPM	198.5–231	4
Elmore County	193 PPM	193–193	2
Idaho County	184 PPM	184–184	1
Jerome County	181 PPM	181–181	1
Gooding County	177 PPM	173–180	2
Butte County	175 PPM	175–175	1

Why local comparisons matter here

Hardness across indexed ZIPs

What the current records support

Utility source mix

Highest eligible city medians

Lowest eligible city medians

Explore Idaho by city

Aberdeen

American Falls

Ammon

Arco

Bonners Ferry

Buhl

Burley

Caldwell

Cascade

Dayton

Driggs

Eagle

Emmett

Filer

Franklin

Fruitland

Genesee

Glenns Ferry

Gooding

Grangeville

Hailey

Hansen

Heyburn

Homedale

Highest regional-evidence county medians