State water index

California water hardness

Search 242 indexed communities and 678 ZIP profiles, then compare the underlying utility, source, distance, and reporting context.

Median regional evidence

254PPM

Very Hard

Indexed range 42.6–1531.5 PPM

ZIP profiles: 678
Cities: 242
Matched utilities: 269
Counties: 42

Understanding California

Why local comparisons matter here

California systems draw from mountain watersheds, large interbasin projects, coastal and inland reservoirs, and many local groundwater basins. Large utilities may change blends seasonally or during drought.

In this index, very hard is the largest category, covering 424 of 549 profiles with hardness data. The state median is 254 PPM, but the full indexed range is 42.6–1531.5 PPM.

State distribution

Hardness across indexed ZIPs

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

Soft · 0–60 PPM32

Moderately hard · 61–120 PPM21

Hard · 121–180 PPM72

Very hard · 181+ PPM424

Evidence coverage

What the current records support

Hardness estimate: 81%
Lead 90th percentile: 100%
Copper 90th percentile: 11%

Low-confidence hardness profiles

241

Research-comparison eligible profiles

Reported source water

Utility source mix

Surface water: 162
Groundwater: 103
Groundwater influenced by surface water: 3
Source not reported: 1

Highest medians

Highest eligible city medians

Lowest medians

Lowest eligible city medians

City directory

Explore California by city

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

242 cities · 678 ZIP profiles

Search city or county

County

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242 cities found

Page 1 of 11

Adelanto

San Bernardino County · 1 ZIP

139PPM regional

County	Median	Range	ZIP profiles
San Diego County	729 PPM	728.5–728.5	53
Santa Barbara County	529 PPM	415–593	10
Ventura County	465 PPM	446–484.5	15
San Luis Obispo County	392 PPM	331–413	6
Imperial County	352 PPM	352–352	6
Contra Costa County	350 PPM	337–362	5
Alameda County	336 PPM	201.5–354	8
San Mateo County	334 PPM	292.5–354	4
Solano County	304 PPM	197.5–335	12
Orange County	262 PPM	254–742	51
Colusa County	262 PPM	253.5–270	2
San Benito County	261 PPM	229–292.5	2

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 California by city

Adelanto

Alhambra

American Canyon

Anaheim

Antioch

Arcadia

Arcata

Arroyo Grande

Atwater

Avenal

Bakersfield

Banning

Benicia

Beverly Hills

Biggs

Blue Lake

Blythe

Brawley

Brea

Brentwood

Brisbane

Buellton

Buena Park

Burbank

Highest regional-evidence county medians