Kahului Water Hardness & Quality Report (2026)
Water Hardness
2.3 grains per gallon
Source
groundwater
pH Level
7.4
neutral = 7.0
Lead
0.004 mg/L
✓ Below action level
TDS
108 mg/L
Est. Daily Cost
$0.11
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 Kahului, your appliances are currently losing 5% efficiency due to mineral buildup.
| Appliance | In Kahului | Soft Water City | Efficiency Loss |
|---|---|---|---|
| Kettle | 8.3 yrs | 8.5 yrs | -2% |
| Washing Machine | 12.1 yrs | 12 yrs | — |
| Water Heater | 14 yrs | 15 yrs | -7% |
Regional Water Comparison
How Kahului compares to its nearest neighbours
| City | Hardness | PFAS (ppt) | Risk | Source |
|---|---|---|---|---|
| ▶ Kahului, Hawaii | 40 mg/L | 1 ppt | 🟢 Soft | groundwater |
| Wailuku, Hawaii | 23 mg/L | 0.7 ppt | 🟢 Soft | groundwater |
| Kihei, Hawaii | 22 mg/L | 0.7 ppt | 🟢 Soft | groundwater |
| Hawai'i Kai, Hawaii | 56 mg/L | 1.2 ppt | 🟢 Soft | groundwater |
| East Honolulu, Hawaii | 31 mg/L | 0.8 ppt | 🟢 Soft | groundwater |
National Benchmark
How Kahului compares to the USA average
| Benchmark | Hardness | Appliance Risk |
|---|---|---|
| ▶ Kahului | 40 mg/L | 🟢 None |
| USA National Avg | 150 mg/L | 🟠 Moderate |
| Badger Top Rated | 8.5 mg/L | 🟢 None |
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What Makes Kahului's Water Unique?
Local geology and source profile
Kahului, Hawaii, in Maui County — a major central Maui commercial and port city (Kahului is a significant Maui County city — the commercial center of Maui and the location of Kahului Airport (the primary airport for Maui — one of the most important regional airports in Hawaii; Kahului Airport serves as the main entry point for the millions of tourists who visit Maui annually and is a critical hub for inter-island travel); Kahului is the hub of central Maui commerce — Queen Ka'ahumanu Center (the largest shopping mall in Maui) and the Maui Mall are major retail destinations; the Kahului Harbor is the primary commercial port for Maui, handling goods for the entire island); Kahului and the surrounding Wailuku–Kahului urban area (together the largest urban concentration on Maui) is the governmental and commercial heart of the island, home of Maui College (one of the University of Hawaii system campuses), and the center of Maui's diverse working-class and professional Hawaiian, Filipino-American, Japanese-American, and mainland transplant population, a diverse Maui County community — draws its municipal water supply via the Maui Department of Water Supply. Water hardness in Kahului measures 40 mg/L — classified as soft.
Kahului's soft supply reflects the central Maui County Haleakala volcanic aquifer's calcareous-poor character. The Haleakala volcanic dike aquifer draws from Quaternary calcareous-poor Haleakala basaltic volcanic with excellent treatment, producing the soft 40 mg/L.
With hardness at 40 mg/L, Kahului residents enjoy soft water. Maui Department of Water Supply consistently delivers water meeting all Hawaii DOH and EPA Safe Drinking Water Act requirements.
Geology & Source: Groundwater from the Maui volcanic dike aquifer (Haleakala watershed) via the Maui Department of Water Supply — the Maui County central Maui Kahului corridor (Quaternary calcareous-poor Haleakala basaltic volcanic — the extremely calcareous-poor central Maui County Haleakala volcanic aquifer; excellent treatment); soft supply at 40 mg/L in Maui County.