State distribution
Hardness across indexed ZIPs
Counts describe published ZIP profiles, not a population-weighted statewide sample.
Soft · 0–60 PPM8
Moderately hard · 61–120 PPM0
Hard · 121–180 PPM0
Very hard · 181+ PPM0
State water index
Hawaii water hardness
Search 24 indexed communities and 28 ZIP profiles, then compare the underlying utility, source, distance, and reporting context.
Median regional evidence
57PPM
Soft
Indexed range 15.6–57.1 PPM
- ZIP profiles
- 28
- Cities
- 24
- Matched utilities
- 34
- Counties
- 4
Understanding Hawaii
Why local comparisons matter here
Hawaii's drinking-water setting is organized island by island, with volcanic aquifers, rainfall gradients, and localized surface-water sources shaping community supplies.
In this index, soft is the largest category, covering 8 of 8 profiles with hardness data. The state median is 57 PPM, but the full indexed range is 15.6–57.1 PPM.
Evidence coverage
What the current records support
- Hardness estimate
- 29%
- Lead 90th percentile
- 100%
- Copper 90th percentile
- 11%
2
Low-confidence hardness profiles
6
Research-comparison eligible profiles
Reported source water
Utility source mix
- Groundwater
- 30
- Surface water
- 4
Highest medians
Highest eligible city medians
Lowest medians
Lowest eligible city medians
City directory
Explore Hawaii by city
Search by city or county, then sort by name, hardness, or ZIP coverage.
24 cities · 28 ZIP profiles
24 cities found
Anahola
Kauai County · 1 ZIP
—
No regional sampleNo active flag
Hana
Maui County · 1 ZIP
—
No regional sampleNo active flag
Hilo
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Honomu
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Kahuku
Honolulu County · 1 ZIP
57PPM regional
Single regional valueNo active flag
Kalaheo
Kauai County · 1 ZIP
—
No regional sampleNo active flag
Kaneohe
Honolulu County · 1 ZIP
57PPM regional
Single regional valueNo active flag
Kaumakani
Kauai County · 1 ZIP
—
No regional sampleNo active flag
Kaunakakai
Maui County · 1 ZIP
—
No regional sampleNo active flag
Kihei
Maui County · 1 ZIP
—
No regional sampleNo active flag
Kualapuu
Maui County · 3 ZIPs
—
No regional sampleNo active flag
Kukuihaele
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Kula
Maui County · 1 ZIP
16PPM regional
Single regional valueNo active flag
Lahaina
Maui County · 1 ZIP
16PPM regional
Single regional valueNo active flag
Laie
Honolulu County · 1 ZIP
57PPM regional
Single regional valueNo active flag
Laupahoehoe
Hawaii County · 3 ZIPs
—
No regional sampleNo active flag
Mokuleia
Honolulu County · 1 ZIP
56PPM regional
Single regional valueNo active flag
Paauilo
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Pahala
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Papaikou
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Pepeekeo
Hawaii County · 1 ZIP
—
No regional sampleNo active flag
Princeville
Kauai County · 1 ZIP
—
No regional sampleNo active flag
Schofield Barracks
Honolulu County · 1 ZIP
57PPM regional
Single regional valueNo active flag
Wahiawa
Honolulu County · 1 ZIP
57PPM regional
Single regional valueNo active flag
County comparison
Highest regional-evidence county medians
| County | Median | Range | ZIP profiles |
|---|---|---|---|
| Honolulu County | 57 PPM | 56.3–57.1 | 6 |
| Maui County | 16 PPM | 15.6–15.6 | 8 |
| Kauai County | — PPM | —–— | 4 |
| Hawaii County | — PPM | —–— | 10 |