Makakilo City Water Hardness & Quality Report (2026)
Water Hardness
3.2 grains per gallon
Source
groundwater
pH Level
7.5
neutral = 7.0
Lead
0.006 mg/L
✓ Below action level
TDS
162.8 mg/L
Est. Daily Cost
$0.15
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 Makakilo City, your appliances are currently losing 7% efficiency due to mineral buildup.
| Appliance | In Makakilo City | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 7.8 yrs | 8.5 yrs | -8% |
| Washing Machine | 11.6 yrs | 12 yrs | -3% |
| Water Heater | 13.4 yrs | 15 yrs | -11% |
Regional Water Comparison
How Makakilo City compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Makakilo City, Hawaii | 55 mg/L | 1.2 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 |
| Kapolei, Hawaii | 49 mg/L | 1.1 ppt | 🟢 Soft | groundwater |
| 'Ewa Gentry, Hawaii | 38 mg/L | 0.9 ppt | 🟢 Soft | groundwater |
National Benchmark
How Makakilo City compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Makakilo City | 55 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Makakilo City's Water Unique?
Local geology and source profile
Makakilo City, Hawaii, in Honolulu County — an unincorporated Honolulu County community adjacent to Kapolei and Ewa Beach on the southwest Oahu plateau — receives its water from the Honolulu Board of Water Supply (BWS), drawing from the Pearl Harbor Aquifer (southwest Oahu) through the southwest Oahu distribution.
The soft 55 mg/L hardness and TDS of 162.8 mg/L (elevated TDS relative to hardness — suggesting minor dissolved chloride from Pacific marine aerosol infiltration) reflect the southwest Oahu volcanic basalt aquifer's moderate softness — consistent with other Oahu BWS communities (Ewa Beach: ~52 mg/L; Kapolei: ~55 mg/L). The Pearl Harbor Aquifer at southwest Oahu is developed in Pleistocene Waianae Volcanics (basalt — slightly weathered, minor calcareous alteration zones), Pleistocene Koolau Basalt (basalt — insoluble primary aquifer), and coastal alluvial caprock (slightly calcareous). The weathered volcanic basalt produces the soft Hawaii supply.
At 55 mg/L, Makakilo City's water is soft — essentially no significant scale forms, soap lathers well, and appliances maintain good efficiency. Annual descaling is sufficient. The PFAS level of 1.2 ppt is very low — the Honolulu County southwest Oahu corridor has limited PFAS legacy, and the Pearl Harbor Naval Station PFAS (AFFF — historic foam use) is primarily contained to the Pearl Harbor basin east of Makakilo.
Geology & Source: Makakilo City in Honolulu County draws from the Oahu Board of Water Supply on the Pearl Harbor Aquifer (Honolulu County, southwest Oahu) — the Pearl Harbor Aquifer at southwest Oahu is developed in Pleistocene Waianae Volcanics basalt and Pleistocene Koolau Basalt (slightly calcareous at contact zones) — Hawaii Honolulu County Pearl Harbor volcanic basalt aquifer produces soft water at 55 mg/L with TDS 162.8 mg/L.