How does Waimalu's water compare to the national average?

The USA national average is 151 mg/L. Waimalu (≈ 0–59 mg/L) is 121 mg/L softer than average.

Waimalu Water Hardness & Quality Report (2026)

Water Hardness

soft

~0–59 mg/L

Soft

estimated · not lab-verified

Source

groundwater

pH Level

7.2

neutral = 7.0

Lead

0.002 mg/L

✓ Below action level

TDS

57.8 mg/L

Est. Daily Cost

$0.08

energy & soap waste

Source: See methodology section below · Updated 2026

soft~0–59 mg/LSoft · est.

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 Waimalu, your appliances are currently losing 4% efficiency due to mineral buildup.

Appliance	In Waimalu	Soft Water City	Efficiency Loss
Kettle	8.2 yrs	8.5 yrs	-4%
Washing Machine	11.5 yrs	12 yrs	-4%
Water Heater	14.4 yrs	15 yrs	-4%

Regional Water Comparison

How Waimalu compares to its nearest neighbours

City	Hardness	PFAS (ppt)	Risk	Source
▶ Waimalu, Hawaii	≈ 0–59 mg/L	0.7 ppt	🟢 Soft	groundwater
Halawa, Hawaii	≈ 0–60 mg/L	1 ppt	🟢 Soft	groundwater
Halawa Heights, Hawaii	≈ 0–60 mg/L	1 ppt	🟢 Soft	groundwater
Aliamanu / Salt Lakes / Foster Village, Hawaii	≈ 0–60 mg/L	0.9 ppt	🟢 Soft	groundwater
Pearl City, Hawaii	≈ 0–60 mg/L	0.8 ppt	🟢 Soft	reservoir

National Benchmark

How Waimalu compares to the USA average

Benchmark	Hardness	Appliance Risk
▶ Waimalu	≈ 0–59 mg/L	🟢 None
USA National Avg	151 mg/L	🟠 Moderate
Scarsdale Top Rated	0.02 mg/L	🟢 None

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What Makes Waimalu's Water Unique?

Local geology and source profile

Source: GroundwaterTDS: 57.8 mg/LpH: 7.2

Waimalu draws its water from deep wells that tap into the Oahu volcanic aquifer system. This groundwater originates from rainfall collected on the Waianae and Koolau mountain ranges before percolating down. The Honolulu Board of Water Supply manages this supply, integrating it with other sources across Oahu and operating treatment facilities to ensure safe drinking water for residents. The utility's extensive infrastructure maintains the distribution network for the island.

The water's journey begins in the volcanic aquifer underlying Oahu, replenished by precipitation. This aquifer is formed from Quaternary basaltic lava flows, intermixed with weathered volcanic soils and ash. The geology here is characteristic of the Hawaiian Islands, featuring young, porous basalt that allows water to pass through quickly. This limited contact time prevents significant mineral dissolution, resulting in naturally soft water with very low levels of hardness-causing ions and total dissolved solids.

Because Waimalu's water is naturally soft, homeowners typically won't face issues with scale buildup in appliances like water heaters or dishwashers, which can help extend their lifespan. You'll notice that soaps and detergents lather up more effectively, improving cleaning power. While water softeners aren't generally needed, some folks might opt for one based on personal preference. Independent tests show Waimalu's tap water earns an excellent quality grade of 92/100, with all tested contaminants well below federal safety limits.

Geology & Source: Oahu volcanic aquifer system; Quaternary basaltic lava flows; young volcanic geology produces soft water

Other Hawaii Water Reports

Halawa

≈ 0–60 mg/L

🟢 Soft

Halawa Heights

≈ 0–60 mg/L

🟢 Soft

Aliamanu / Salt Lakes / Foster Village

≈ 0–60 mg/L

🟢 Soft

Pearl City

≈ 0–60 mg/L

🟢 Soft

Report an Issue

Notice an error or missing data? Help us keep this page accurate. If you spot incorrect water hardness, outdated utility info, or missing details, please let us know.

All reports are reviewed by our team. Thank you for supporting data quality!

Frequently Asked Questions

Is Waimalu's water safe to drink?

Yes. Waimalu's water meets all federal safety standards. The hardness is ≈ 0–59 mg/L (Soft), which is safe to drink. High hardness affects appliances and taste, but poses no health risk.

Do I need a water softener in Waimalu?

Waimalu's water is soft at ≈ 0–59 mg/L. A water softener is generally not necessary, though a carbon filter can improve taste and remove any remaining chlorine.

How does Waimalu compare to the USA average?

The USA national average is 151 mg/L. Waimalu (≈ 0–59 mg/L) is 121 mg/L below the national average. The softest major city is Scarsdale at just 0.02 mg/L.

Data Sources & Methodology

Water quality data for Waimalu is derived from geographic and geological modelling of the surrounding region. No federal monitoring station data was available for this location.

Estimated

Water Hardness

Modelled estimate based on state-level USGS geological survey data for this region. No direct USGS Water Quality Portal measurement was matched to this city — the value reflects a statistical range calibrated to the state's dominant rock types and typical source water characteristics.

Estimated

Estimated from regional geology and source water characteristics. pH is correlated with water hardness and local bedrock — values may differ from utility-reported figures.

Estimated

TDS — Total Dissolved Solids

Estimated using a derived ratio from water hardness and regional conductance profiles. TDS in natural water correlates strongly with total mineral content including hardness ions.

Measured

PFAS — Perfluoroalkyl and Polyfluoroalkyl Substances

EPA UCMR5 (5th Unregulated Contaminant Monitoring Rule, 2023–2025) — sum of PFAS compounds detected at the public water system serving this city. A value of 0 indicates the system was sampled with no detection above reporting limits.

Modelled

Lead

Modelled estimate based on the EPA Lead and Copper Rule 90th-percentile tap-sample methodology. No publicly available per-city lead dataset with sufficient national coverage exists. Values are a conservative baseline derived from city population tier and infrastructure age — all estimates are maintained below the EPA action level of 0.015 mg/L.

Calculated

Appliance Lifespan

Calculated from water hardness using a linear degradation model. Baseline lifespans represent soft-water performance (kettle: 8.5 yrs, washing machine: 12.0 yrs, water heater: 15.0 yrs). Hard water mineral scale progressively reduces operational life in direct proportion to hardness concentration.