Washington vs Idaho: Whose Tap Water Is Harder?
Water Hardness in Washington (70 PPM) vs Idaho (100 PPM) — a 35% gap between neighbors, explained with July 2026 data.
Washington and Idaho share a border, but for water hardness they don't share much else: Washington averages 70 PPM (rank #9 of 51) and Idaho averages 100 PPM (rank #15) as of July 2026 — a 35% gap between neighbors.
| Washington | Idaho | U.S. benchmark | |
|---|---|---|---|
| Average hardness | 70 PPM | 100 PPM | 120 PPM |
Washington in context
Washington averages 70 PPM — "moderately hard" on the USGS scale and 42% softer than the national average of 120 PPM (rank #9 of 51, 1 = softest). Most households here get by fine without a softener, though scale slowly accumulates in heaters and kettles.
Idaho in context
Idaho averages 100 PPM — "moderately hard" on the USGS scale and 17% softer than the national average of 120 PPM (rank #15 of 51, 1 = softest). Most households here get by fine without a softener, though scale slowly accumulates in heaters and kettles.
Full local breakdowns: Washington · Idaho · all states ranked.
State averages hide huge local swings. A certified home water test kit tells you your exact hardness and what's dissolved in your water — before you spend a dollar on treatment.
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