Hardest Water in Hawaii
7 cities ranked by water hardness. Honolulu tops the list at 80 PPM.
Hawaii's water hardness varies significantly by city and water source. The state average across our database is 53 PPM, which is relatively soft. Most homes do not need a water softener. 0% of cities we track in Hawaii have hardness above 120 PPM.
Waikiki has the softest water at just 20 PPM. No softener is needed.
| # | City | PPM | GPG | Level | Softener? |
|---|---|---|---|---|---|
| 1 | Honolulu | 80 | 4.7 | Moderately Hard | Optional |
| 2 | Pearl City | 75 | 4.4 | Moderately Hard | Optional |
| 3 | Kapolei | 70 | 4.1 | Moderately Hard | Optional |
| 4 | Kailua | 65 | 3.8 | Moderately Hard | Optional |
| 5 | Hilo | 30 | 1.8 | Slightly Hard | No |
| 6 | Kailua-Kona | 30 | 1.8 | Slightly Hard | No |
| 7 | Waikiki | 20 | 1.2 | Slightly Hard | No |
Frequently Asked Questions
What is the average water hardness in Hawaii?
Across 7 cities in our database, the average water hardness in Hawaii is 53 PPM (3.1 GPG). This ranges from 20 PPM in Waikiki to 80 PPM in Honolulu.
Do I need a water softener in Hawaii?
It depends on your city. 0% of Hawaii cities in our database (0 of 7) have hardness above 120 PPM where a softener provides measurable benefit. Check your specific city above.
Which Hawaii city has the softest water?
Waikiki has the softest water in Hawaii at 20 PPM (1.2 GPG). No water softener is needed at this level.
What causes hard water in Hawaii?
Hard water in Hawaii is caused by dissolved calcium and magnesium from the local geology. Most of the state has favorable geology with granite, metamorphic, or volcanic rock that contributes minimal dissolved minerals.