West Side Maui Water Report
Covering Lahaina, Wahikuli, Honokōwai, Kahana, and Nāpili, with a separate section for Kapalua. Compiled from EWG's Tap Water Database and the County of Maui Department of Water Supply. Your exact numbers can vary by address — book a consult and we'll confirm your specific system.
Where your water comes from
West Side's water comes from a mix of sources — surface water from Kanahā Stream (Lahaina Water Treatment Facility) and Honokōhau Ditch (Māhinahina Water Treatment Facility), plus groundwater wells at Kanahā, Nāpili, Waipuka, and Honokōhau. Serving about 20,000 residents, it's the third-largest system on the island.
Baseline water quality — separate from the fire recovery
The data below reflects this system's ongoing, baseline water testing — separate from the post-fire advisory, which has been resolved. This system carries 27 total contaminants, 14 of which exceed EWG's health guidelines, including the highest 1,2,3-Trichloropropane reading of any Maui system we've profiled.
Agricultural & Industrial Legacy
1,2,3-Trichloropropane (TCP)
Cancer riskWhat is this and where does it come from?
A potent carcinogen used historically as a soil fumigant in agricultural regions — this is the highest TCP reading of any Maui system we've profiled, consistent with West Maui's plantation-era agricultural history.
DBCP (1,2-Dibromo-3-chloropropane)
Cancer & fertility riskWhat is this and where does it come from?
A pesticide fumigant banned in the 1970s after it was found to cause sterility in exposed male workers. Still detected in West Side testing from past agricultural use.
Hexavalent Chromium
Cancer riskWhat is this and where does it come from?
A carcinogen that can come from industrial pollution or occur naturally in mineral deposits and groundwater.
Disinfection Byproducts
Haloacetic Acids (HAA5)
Cancer riskWhat is this and where does it come from?
A group of five chemicals formed during disinfection. Linked to cancer risk and potential harm during pregnancy.
Total Trihalomethanes (TTHMs)
Cancer riskWhat is this and where does it come from?
Forms when chlorine reacts with naturally occurring organic matter — a byproduct of disinfection, not outside contamination.
Trichloroacetic Acid
Cancer riskWhat is this and where does it come from?
A haloacetic acid formed during disinfection.
Bromodichloromethane
Cancer riskWhat is this and where does it come from?
One of four trihalomethanes formed during disinfection. Linked to cancer risk and possible harm to fetal growth.
Bromochloroacetic Acid
Cancer riskWhat is this and where does it come from?
A haloacetic acid formed during disinfection.
Dibromochloromethane
Cancer riskWhat is this and where does it come from?
One of four trihalomethanes formed during disinfection.
Dibromoacetic Acid
Cancer riskWhat is this and where does it come from?
A haloacetic acid formed during disinfection.
Chloroform
Cancer riskWhat is this and where does it come from?
The most common trihalomethane, formed during chlorine disinfection.
Dichloroacetic Acid
Cancer riskWhat is this and where does it come from?
A haloacetic acid formed during disinfection.
Bromoform
Cancer riskWhat is this and where does it come from?
One of four trihalomethanes formed during disinfection.
Endocrine Disruptor
Chlorate
Thyroid functionWhat is this and where does it come from?
Forms as a byproduct of disinfection. Impairs thyroid function, making exposure most concerning during pregnancy and childhood.
What this means for you
Your water meets every federal and state legal limit. But "legal" reflects standards that haven't been updated in nearly 20 years, not the latest independent health science. West Side's profile is shaped by two things: decades-old agricultural chemical residue (TCP, DBCP) from the region's plantation history, and the same disinfection byproducts found across Maui's chlorinated systems. This baseline predates and is separate from the 2023 fire event — that contamination has been tested, confirmed resolved, and the advisory fully lifted.
What's in your pipes matters too. These results describe the water as it leaves the utility's system. On the way to your tap it can pick up lead, copper, or other metals from older city plumbing or from the pipes, fixtures, and solder in your own home. A utility's results can't see that, but testing your tap can.
PFAS: tested, not detected
This system has been tested for PFAS ("forever chemicals") and none were detected.
Kapalua
Kapalua is not on the County system
Water in the Kapalua Resort area, including its private homes and estates, is provided by Hawaii Water Service's Kapalua District, a privately owned utility regulated by the Hawaiʻi Public Utilities Commission. That means the West Side data above does not describe Kapalua water. The District draws from two groundwater wells in the Honolua Aquifer, fed by the Puʻu Kukui watershed, and chlorinates the water before distribution. Homes outside the resort area on private wells or catchment have a different picture and are best understood through testing.
Total Trihalomethanes (TTHMs)
Cancer riskWhat is this and where does it come from?
Forms when chlorine reacts with naturally occurring organic matter. It is a byproduct of disinfection, not outside contamination. This is the one contaminant in Kapalua's published results that we compare to an EWG health guideline, and it is a much lower reading than the West Side system above.
Also reported for Kapalua (2025)
Nitrate 0.23 ppm (legal limit 10 ppm), fluoride 0.06 ppm (legal limit 4 ppm), sodium 22 ppm, and chlorine at an average of 0.4 ppm. All are within legal limits.
Lead, copper, and PFAS: not detected
Lead and copper were not detected in 2024 sampling, with none of 21 samples over the action level. No PFAS has been detected in any active source, based on 2023 testing. These results describe the utility's water; lead can also come from plumbing inside the home.
What we can't confirm
Kapalua's published report lists only the substances that were detected, and it is not part of EWG's Tap Water Database. A contaminant that isn't listed was most likely not found, but the report doesn't say so directly. If you want certainty about agricultural legacy chemicals or anything else, independent testing of your own tap is the way to get it.
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We'll confirm which utility serves your address, walk through your results, and recommend the right filtration for your home — no pressure, just answers. Rebuilding or otherwise impacted by the fires? Ask us about our most generous discounts when you book.
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