Downtown Water Hardness & Quality Report (2026)
Water Hardness
2 grains per gallon
Source
groundwater
pH Level
7.3
neutral = 7.0
Lead
0.004 mg/L
✓ Below action level
TDS
91.4 mg/L
Est. Daily Cost
$0.09
energy & soap waste
Source: USGS Water Quality Portal · Updated 2026
0–60
mg/L
Soft
61–120
mg/L
Moderately Hard
121–180
mg/L
Hard
180+
mg/L
Very Hard
Appliance Damage Report
In Downtown, your appliances are currently losing 5% efficiency due to mineral buildup.
| Appliance | In Downtown | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 8.4 yrs | 8.5 yrs | -1% |
| Washing Machine | 12.3 yrs | 12 yrs | — |
| Water Heater | 14.2 yrs | 15 yrs | -5% |
Regional Water Comparison
How Downtown compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Downtown, Hawaii | 35 mg/L | 0.9 ppt | 🟢 Soft | groundwater |
| Honolulu, Hawaii | 67.5 mg/L | 1.3 ppt | 🟡 Moderately Hard | groundwater |
| Ala Moana - Kaka'ako, Hawaii | 66 mg/L | 1.3 ppt | 🟡 Moderately Hard | groundwater |
| Waikiki, Hawaii | 20 mg/L | 0.7 ppt | 🟢 Soft | groundwater |
| McCully - Moiliili, Hawaii | 20.5 mg/L | 0.7 ppt | 🟢 Soft | groundwater |
National Benchmark
How Downtown compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Downtown | 35 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Downtown's Water Unique?
Local geology and source profile
Downtown Honolulu, Hawaii, in Honolulu County — the Honolulu County urban core adjacent to Chinatown and Kakaako on the central Oahu coastal plain — receives its water from the Board of Water Supply, drawing from the Pearl Harbor basalt aquifer (Honolulu County) through the Oahu central distribution.
The very soft 35 mg/L hardness and low TDS of 91.4 mg/L reflect the Oahu central plain Pearl Harbor basalt aquifer supply's very soft character — the Quaternary Ko'olau Basalt and Waianae Basalt contribute insoluble dilution with minimal calcareous contact, among the softest water in Hawaii (compare Palolo HI: 27/66.7 in the windward Ko'olau supply softer; Downtown Honolulu similarly very soft from the Pearl Harbor central plain basalt aquifer). The Pearl Harbor aquifer at Honolulu County — Quaternary Ko'olau Basalt (insoluble — primary dilutant), Quaternary Waianae Basalt (insoluble — secondary dilutant), and Holocene coastal alluvium (slightly calcareous — trace TDS).
At 35 mg/L, Downtown Honolulu's water is very soft — scale forms very slowly in appliances, dishwashers remain efficient, and no softening is needed. Annual descaling is appropriate. The PFAS level of 0.9 ppt is very low — no filtration urgently required, warrants routine monitoring only. Downtown Honolulu's PFAS level is among the lowest in the dataset, reflecting its volcanic island aquifer supply.
Geology & Source: Downtown in Honolulu County draws from the Board of Water Supply on the Pearl Harbor basalt aquifer (Honolulu County, Oahu central plain, Hawaii) — the Pearl Harbor aquifer at Honolulu County is developed in Quaternary Ko'olau Basalt (insoluble) and Quaternary Waianae Basalt (insoluble) — Hawaii Honolulu County Pearl Harbor basalt Quaternary insoluble volcanic supply produces very soft water at 35 mg/L with TDS 91.4 mg/L.