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 indexed hardness

189PPM

Very Hard

Indexed range 3.3–728.5 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 460 of 678 profiles with hardness data. The state median is 189 PPM, but the full indexed range is 3.3–728.5 PPM.

State distribution

Hardness across indexed ZIPs

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

Soft · 0–60 PPM34

Moderately hard · 61–120 PPM6

Hard · 121–180 PPM178

Very hard · 181+ PPM460

Evidence coverage

What the current records support

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

129

Low-confidence hardness profiles

127

Nearest site more than 25 miles away

Reported source water

Utility source mix

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

Highest medians

Hardest indexed cities

Lowest medians

Softest indexed cities

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

180PPM

County	Median	Range	ZIP profiles
San Diego County	729 PPM	167–728.5	53
Santa Barbara County	415 PPM	406–534	10
San Luis Obispo County	405 PPM	404.5–446	6
Imperial County	390 PPM	390–403.5	6
Ventura County	336 PPM	241–444.5	15
Kern County	298 PPM	69.1–565	14
Monterey County	276 PPM	268–291	5
Santa Cruz County	274 PPM	256–282.5	4
Santa Clara County	271 PPM	213–282.5	49
San Joaquin County	265 PPM	175–299	21
Alameda County	250 PPM	241–271	8
Stanislaus County	237 PPM	162–274	16

Why local comparisons matter here

Hardness across indexed ZIPs

What the current records support

Utility source mix

Hardest indexed cities

Softest indexed cities

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 indexed county medians