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Water Hardness in Kahului, HI

Hawaii · 1 zip codes · 6 matched water systems

19 PPM
1.1 GPG
Soft
0Soft60120180300+
High Confidence — USGS Monitoring

Dataset updated March 9, 20266 matched water systems in the city rollupIndividual systems and ZIPs can differ. Methodology

Source context

How this city reading is built

This city reading is a weighted rollup across 6 matched water systems and 1 ZIP code. Citywide readings are useful for comparison, but individual utility zones and ZIPs can differ.

Source basis
6 USGS-backed sources
6 matched systems total for this city; USGS monitoring is used where treated-water reports are unavailable.
Water source profile
Primarily surface water
Surface-water hardness can shift with reservoirs, runoff, season, and treatment. This profile is weighted by known population served across matched systems.
Data recency
March 9, 2026
Dataset rebuilt March 9, 2026; individual utility reporting years can vary.

Hardness is a mineral-content reading, not a drinking-water safety rating. Use it for scale, appliance, and softener decisions; check your utility report or test your tap before sizing treatment equipment. See how we calculate local readings.

Water Systems in Kahului

These systems are matched to Kahului, HI. Citywide readings are useful for comparison, but the system serving a specific address may differ from the city average.

6 water systems
PWSID is the public water system identifier. Data Source shows whether the hardness value comes from a treated-water report, USGS monitoring, or a local estimate; source year is shown when available.
Wailuku
HI0000212
Soft
19 PPMsurface water74,511 servedHigh Confidence — USGS Monitoring
Makawao
HI0000213
Soft
19 PPMsurface water29,868 servedHigh Confidence — USGS Monitoring
Lahaina
HI0000214
Soft
19 PPMsurface water20,065 servedHigh Confidence — USGS Monitoring
Mahanalua Nui Subdivison
HI0000251
Soft
19 PPMgroundwater606 servedHigh Confidence — USGS Monitoring
Olowalu
HI0000209
Soft
19 PPMgroundwater100 servedHigh Confidence — USGS Monitoring
Showing the first 5 systems. Expand to review all matched systems.

Zip Codes in Kahului, HI

9673219

What This Means For You

Recommendations are based on the displayed hardness reading. Confirm your tap reading before sizing or buying treatment equipment.

Your Water Is Soft

Your water hardness is in the soft range. You likely don't need a water softener. Enjoy your naturally soft water!

Know your water hardness?

If you've tested your water or have your utility's CCR report, share your reading to help us improve accuracy for Kahului, HI.

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Frequently Asked Questions

How hard is the water in Kahului, HI?

The citywide weighted average water hardness in Kahului, HI is 19 PPM (1.1 GPG), classified as soft. This is based on 6 matched water systems.

Do I need a water softener in Kahului, HI?

At 19 PPM, the citywide average is relatively soft. A water softener is generally not necessary.

Is hard water in Kahului, HI safe to drink?

Water hardness itself is a mineral-content reading, not a drinking-water safety rating. Calcium and magnesium are naturally occurring minerals, but you should check your utility's Consumer Confidence Report for contaminant and compliance information.

How many water systems serve Kahului, HI?

Kahului, Hawaii is served by 6 matched water systems across 1 zip code.

Learn More About Your Water

Water Hardness Scale: PPM and GPG Chart

Use the USGS water hardness scale to compare PPM, GPG, and mg/L levels from soft to very hard water.

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How to Test Water Hardness at Home

Compare free lookups, soap tests, test strips, liquid drop kits, and lab tests for measuring water hardness.

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