State distribution
Hardness across indexed ZIPs
Counts describe published ZIP profiles, not a population-weighted statewide sample.
Soft · 0–60 PPM13
Moderately hard · 61–120 PPM0
Hard · 121–180 PPM1
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 indexed hardness
57PPM
Soft
Indexed range 15.6–125 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 13 of 14 profiles with hardness data. The state median is 57 PPM, but the full indexed range is 15.6–125 PPM.
Evidence coverage
What the current records support
- Hardness estimate
- 50%
- Lead 90th percentile
- 100%
- Copper 90th percentile
- 11%
8
Low-confidence hardness profiles
5
Nearest site more than 25 miles away
Reported source water
Utility source mix
- Groundwater
- 30
- Surface water
- 4
Highest medians
Hardest indexed cities
- 1. Kaunakakai125 PPM
- 2. Kahuku57 PPM
- 3. Kaneohe57 PPM
- 4. Kualapuu57 PPM
- 5. Laie57 PPM
Lowest medians
Softest indexed cities
- 1. Lahaina16 PPM
- 2. Kula16 PPM
- 3. Kihei16 PPM
- 4. Hana16 PPM
- 5. Wahiawa57 PPM
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 hardness estimateNo active flag
Hana
Maui County · 1 ZIP
16PPM
Single indexed valueNo active flag
Hilo
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Honomu
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Kahuku
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
Kalaheo
Kauai County · 1 ZIP
—
No hardness estimateNo active flag
Kaneohe
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
Kaumakani
Kauai County · 1 ZIP
—
No hardness estimateNo active flag
Kaunakakai
Maui County · 1 ZIP
125PPM
Single indexed valueNo active flag
Kihei
Maui County · 1 ZIP
16PPM
Single indexed valueNo active flag
Kualapuu
Maui County · 3 ZIPs
57PPM
Range 55.2–57.1No active flag
Kukuihaele
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Kula
Maui County · 1 ZIP
16PPM
Single indexed valueNo active flag
Lahaina
Maui County · 1 ZIP
16PPM
Single indexed valueNo active flag
Laie
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
Laupahoehoe
Hawaii County · 3 ZIPs
—
No hardness estimateNo active flag
Mokuleia
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
Paauilo
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Pahala
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Papaikou
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Pepeekeo
Hawaii County · 1 ZIP
—
No hardness estimateNo active flag
Princeville
Kauai County · 1 ZIP
—
No hardness estimateNo active flag
Schofield Barracks
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
Wahiawa
Honolulu County · 1 ZIP
57PPM
Single indexed valueNo active flag
County comparison
Highest indexed county medians
| County | Median | Range | ZIP profiles |
|---|---|---|---|
| Honolulu County | 57 PPM | 57.1–57.1 | 6 |
| Maui County | 35 PPM | 15.6–125 | 8 |
| Kauai County | — PPM | —–— | 4 |
| Hawaii County | — PPM | —–— | 10 |