Makakilo 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
251.1 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 Makakilo, your appliances are currently losing 10% efficiency due to mineral buildup.
| Appliance | In Makakilo | 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 Makakilo compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Makakilo, Hawaii | 75.5 mg/L | 1.5 ppt | 🟡 Moderately Hard | groundwater |
| Makakilo City, Hawaii | 55 mg/L | 1.2 ppt | 🟢 Soft | 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 compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Makakilo | 75.5 mg/L | 🟡 Low |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Makakilo's Water Unique?
Local geology and source profile
Makakilo, Hawaii, in Honolulu County — an unincorporated Honolulu County community adjacent to Kapolei and Ewa Beach on the Ewa Plain of southwest Oahu — receives its municipal water from the Honolulu Board of Water Supply (BWS), drawing from the Pearl Harbor Aquifer (Oahu basal aquifer system beneath the Ewa-Makakilo Plain).
The soft 75.5 mg/L hardness and TDS of 251.1 mg/L reflect Oahu's basaltic volcanic island aquifer character. The Pearl Harbor Aquifer beneath Makakilo is developed within the Pleistocene Ko'olau Basalt and Pliocene Waianae Basalt — both are olivine tholeiite basalt flows (low-calcium, non-carbonate volcanic rock). The fresh groundwater is basal — floating on denser saltwater as a fresh-water lens within the volcanic basalt. The low-mineral basalt matrix produces the soft, low-TDS water characteristic of Hawaiian island aquifers.
At 75.5 mg/L, Makakilo's water is soft — essentially no scale forms, soap lathers abundantly, and appliances maintain good efficiency. Annual descaling is sufficient. The PFAS level of 1.5 ppt is among the lowest in the USA — well below any regulatory threshold and reflecting Oahu's limited industrial PFAS footprint. No special filter is required for PFAS at this level, though a certified filter can be used for peace of mind.
Geology & Source: Makakilo in Honolulu County draws from the Honolulu Board of Water Supply on the Oahu basal aquifer (Pleistocene-Pliocene Waianae Basalt and Ko'olau Basalt, Pearl Harbor aquifer) — Hawaii's basaltic shield volcanic formations produce soft groundwater — Oahu Pleistocene basalt volcanic aquifer produces soft water at 75.5 mg/L with TDS 251 mg/L in this Honolulu County Hawaii community.