Nanakuli Water Hardness & Quality Report (2026)
Water Hardness
4.4 grains per gallon
Source
groundwater
pH Level
7.7
neutral = 7.0
Lead
0.009 mg/L
✓ Below action level
TDS
253.1 mg/L
Est. Daily Cost
$0.20
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 Nanakuli, your appliances are currently losing 10% efficiency due to mineral buildup.
| Appliance | In Nanakuli | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 7.1 yrs | 8.5 yrs | -16% |
| Washing Machine | 10.8 yrs | 12 yrs | -10% |
| Water Heater | 12.6 yrs | 15 yrs | -16% |
Regional Water Comparison
How Nanakuli compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Nanakuli, Hawaii | 76 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
| Waianae, Hawaii | 15 mg/L | 0.6 ppt | 🟢 Soft | groundwater |
| Makakilo, Hawaii | 75.5 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
| Makakilo / Kapolei / Honokai Hale, Hawaii | 35.5 mg/L | 0.9 ppt | 🟢 Soft | groundwater |
| Makakilo City, Hawaii | 55 mg/L | 1.2 ppt | 🟢 Soft | groundwater |
National Benchmark
How Nanakuli compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Nanakuli | 76 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Nanakuli's Water Unique?
Local geology and source profile
Nanakuli, Hawaii, in Honolulu County — a Honolulu County community adjacent to Waianae and Kapolei on the leeward Oahu coast — receives its water from the Board of Water Supply, drawing from the Waianae or Ewa groundwater (Honolulu County) through the leeward Oahu distribution.
The soft 76 mg/L hardness and TDS of 253.1 mg/L reflect the leeward Oahu Honolulu County basalt-coral aquifer supply's moderate character — the Quaternary Waianae Basalt provides insoluble dilution, while the Ewa calcareous coral and basalt dissolution in the leeward dry climate contributes moderate TDS and slight hardness, typical of the leeward Oahu communities (compare Honolulu metro: ~50-80 mg/L on the Ko'olau basalt supply; Nanakuli at the soft range for the leeward Waianae zone). The Waianae-Ewa aquifer at Honolulu County — Quaternary Waianae Basalt (insoluble — primary dilutant), Quaternary Ewa calcareous coral (slightly calcareous — primary hardness contributor), and Oahu saltwater mixing (chloride — TDS contributor).
At 76 mg/L, Nanakuli's water is soft — scale forms very slowly in appliances, dishwashers remain efficient, and no softening is needed. Annual descaling is appropriate. The PFAS level of 1.5 ppt is very low — no filtration urgently required, warrants routine monitoring only.
Geology & Source: Nanakuli in Honolulu County draws from the Board of Water Supply on the Waianae or Ewa groundwater (Honolulu County, Oahu leeward coast, Hawaii) — the Waianae-Ewa aquifer at Oahu is developed in Quaternary Waianae Basalt (insoluble) and Quaternary Ewa calcareous coral (slightly calcareous) — Hawaii Honolulu County Waianae basalt-coral Quaternary supply produces soft water at 76 mg/L with TDS 253.1 mg/L.