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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Comprehensive water safety analysis • Updated June 2026
Honolulu's water quality score of 70/100 indicates fair quality with several contaminants worth monitoring.
•All 3 historical violation(s) in Honolulu have been resolved.
Some Concerns. Consider a water filter for extra protection. Score: 70/100.
Want to understand your score better? Learn how scores are calculated →
Is your neighbor's water better? See how Honolulu's grade of B- (70/100) stacks up.
Guides matched to the contaminants found in your water
Above 50% of EPA limits
| Contaminant | Level Detected | EPA Limit | % of Limit | Status |
|---|---|---|---|---|
| Total Trihalomethanes | 42.52 ug/L | 80.00 ug/L | 53.2% | Warning |
9 contaminants tested • EPA SDWIS data • Click any contaminant for details
| Contaminant | Level Detected | EPA Limit | % of Limit | Status |
|---|---|---|---|---|
| Total Trihalomethanes | 42.52 ug/L | 80.00 ug/L | 53.2% | Warning |
| Arsenic | 0.0045 mg/L | 0.010 mg/L | 44.8% | Safe |
| Nitrate | 4.00 mg/L | 10.00 mg/L | 40.0% | Safe |
| Nitrite | 0.369 mg/L | 1.00 mg/L | 36.9% | Safe |
| Fluoride | 1.08 mg/L | 4.00 mg/L | 27.0% | Safe |
| Copper | 0.345 mg/L | 1.30 mg/L | 26.6% | Safe |
| Chromium | 0.026 mg/L | 0.100 mg/L | 26.4% | Safe |
| Haloacetic Acids | 15.59 ug/L | 60.00 ug/L | 26.0% | Safe |
| Mercury | 0.0004 mg/L | 0.0020 mg/L | 19.4% | Safe |
Based on detected contaminants in your water
Best for Honolulu. Removes 95-99% of contaminants including heavy metals, PFAS, and nitrates.
APEC Water Systems RO — ~$200 on AmazonRemoves chlorine, improves taste, and filters many organic compounds. Great starting point.
| Filter Type | Best For | Typical Price |
|---|---|---|
| Reverse Osmosis | Lead, PFAS, arsenic, nitrates (95-99% removal) | $150-300 |
| Under-sink carbon block | Chlorine, VOCs, many organics; some lead/PFAS models | $100-250 |
| Pitcher / faucet carbon | Chlorine, taste; NSF 53 models also reduce lead | $20-50 |
See our full water filter comparison for certified products matched to specific contaminants.
Our data covers your city's water system, but contaminants can vary at the tap. A home water test gives you exact results for your faucet.
Get a Certified Home Water Test — Tap ScoreWe may earn a commission when you purchase through our links, at no extra cost to you. All recommendations are based on our independent analysis of Honolulu's water quality data.
Specific to the contaminants found in Honolulu's EPA-reported water data
Arsenic has been detected in Honolulu's water supply. Long-term arsenic exposure, even at levels near EPA limits, is associated with increased risk of skin, lung, bladder, kidney, and liver cancers. Arsenic exposure can also cause cardiovascular disease, diabetes, and neurological effects. Skin changes like thickening and pigmentation may indicate chronic exposure. Reverse osmosis filtration is highly effective at removing arsenic from drinking water.
Elevated nitrate levels in Honolulu's water pose particular risk to infants under six months. Nitrates can cause methemoglobinemia ("blue baby syndrome"), a condition where the blood cannot carry sufficient oxygen. Symptoms include bluish skin color, shortness of breath, and in severe cases, death. Formula-fed infants are at greatest risk. Pregnant women should also limit nitrate exposure. Boiling water does NOT remove nitrates—it actually concentrates them. Reverse osmosis or distillation systems effectively remove nitrates.
Past violations for Honolulu's water system
monitoring
Chromium - 2/4/2022
Resolvedother
Haloacetic Acids - 2/3/2025
ResolvedMCL
Haloacetic Acids - 2/4/2024
ResolvedHow to contact your water provider and access official reports
The primary water provider for Honolulu is HONOLULU WATER SYSTEM (Public Water System ID: HI801208), serving approximately 343,284 residents. This utility is responsible for treating, testing, and delivering drinking water that meets EPA standards under the Safe Drinking Water Act. As a regulated public water system, it is required to conduct regular testing for over 90 contaminants and publish results in an annual Consumer Confidence Report (CCR) that must be made available to all customers by July 1 each year.
Your water utility is legally obligated to notify customers within 24 hours of any violation that poses an immediate health risk, and within 30 days for less urgent violations. If you are concerned about your water quality, you have the right to request testing data from your utility at any time. For independent verification, you can have your water tested at the tap by a state-certified laboratory. The EPA maintains a list of certified labs by state at epa.gov/dwlabcert. Home testing is particularly important because it captures contamination from your household plumbing that utility testing at distribution points would not detect.
Honolulu Water Quality Score
Based on EPA contaminant data and compliance records
Honolulu's water contains Total Trihalomethanes at 53% of the EPA limit.
Best for Arsenic Removal
APEC Reverse Osmosis System
Multi-stage RO removes arsenic to safe levels — the EPA-recommended treatment for arsenic.
Check Price on AmazonNot sure what filter you need?
Get a lab-certified water test to know exactly what's in your tap water.
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Based on contaminants detected in your water, these resources may be helpful:
Find the right filter for your Honolulu water quality needs:
Understand the contaminants that may be present in Honolulu's water supply and their health effects.
Matched to the contaminants actually detected in Honolulu's water
Arsenic was detected in Honolulu's water — reverse osmosis is highly effective at removing it.
We may earn a commission when you purchase through our links, at no extra cost to you.
Understand your water better with our in-depth guides on contaminants, filtration, and water safety.
Honolulu's 70/100 score measured against the Hawaii average and the national benchmark
Honolulu stays within every EPA legal limit, but Total Trihalomethanes sits at 53.2% of its limit — the single contaminant most worth watching here.
Compared with the Hawaii average of 81.2, Honolulu scores 11.2 points below the state average. Among the 15 Hawaii cities we track, Honolulu ranks #13 — in the bottom third of the state.
Against the national benchmark of 80.8/100, Honolulu comes in 10.8 points below the national average. The contaminant closest to its limit here is Total Trihalomethanes, measured at 53.2% of the EPA limit — high enough that residents wanting extra protection should consider targeted filtration. At the other end, Mercury is its cleanest reading at just 19.4% of the limit.
For Honolulu residents, the water is legally safe, but the elevated readings above are worth a quick decision: households with infants, pregnant women, or anyone immunocompromised get the most benefit from a targeted filter, while others may simply prefer it for taste and peace of mind.
Honolulu's drinking water is managed by HONOLULU WATER SYSTEM, which serves approximately 343,284 residents through a combination of surface and groundwater sources. Our analysis of 9 tested contaminants reveals a quality score of 70/100, placing Honolulu at a fair level relative to other Hawaii communities.
While Honolulu's water meets all EPA maximum contaminant levels, 1 contaminant is present at elevated levels (above 50% of EPA limits). This doesn't necessarily indicate a health risk, but residents who want additional protection may benefit from a home water filter.
Honolulu's water system has 3 documented EPA violations in its compliance history. All have since been resolved, indicating the utility has addressed past issues. Compliance history is one of the factors in our scoring methodology.
This report is based on data from the EPA Safe Drinking Water Information System (SDWIS) and the EPA Enforcement and Compliance History Online (ECHO) database. Our scoring algorithm weighs contaminant analysis (50%), compliance history (30%), and infrastructure factors (20%). Data is sourced directly from public EPA records and Consumer Confidence Reports. We are an independent resource with no affiliation to water utilities or government agencies. Learn more about our methodology.
Common questions from Honolulu, Hawaii residents about their drinking water
Honolulu's tap water has some concerns with a quality score of 70/100 (Grade B-). While all contaminants are technically within EPA limits, 1 are at elevated levels. We recommend using a certified water filter for drinking and cooking water, especially in households with children, pregnant women, or immunocompromised individuals.
Honolulu's water has been tested for 9 contaminants spanning inorganic chemicals, disinfection byproducts, organic compounds, radionuclides, and microorganisms. No contaminants exceed EPA limits, but 1 are at elevated levels above 50% of EPA Maximum Contaminant Levels, including Total Trihalomethanes. See the full contaminant breakdown table above for detailed measurements and EPA limit comparisons.
Honolulu has a water quality score of 70/100, earning a grade of B-. This score is calculated using EPA SDWIS data and weighs three factors: contaminant levels (50% of score), regulatory compliance history (30%), and infrastructure factors (20%). The national average is approximately 72/100. Honolulu's score of 70 is 2 points below the national average, suggesting residents should take additional precautions such as using a water filter. Learn more about how scores are calculated.
Based on Honolulu's water quality profile, we recommend a reverse osmosis (RO) system for the most comprehensive filtration. Arsenic is present, and RO systems typically remove over 95% of arsenic. A quality RO system costs approximately $150-300 and is installed under the kitchen sink. Even in cities with good water quality, a filter provides an additional layer of protection against contaminants that may enter water from your home's plumbing. View our water filter comparison guide for specific product recommendations.
Honolulu's primary water system, HONOLULU WATER SYSTEM (PWS ID: HI801208), sources water from a combination of surface and groundwater sources, which provides resilience in the water supply but means the utility must manage treatment for the different contamination profiles of each source type. This system serves approximately 343,284 residents.
Lead testing in Honolulu shows levels within EPA action level guidelines. However, lead contamination is primarily a household plumbing issue rather than a water source issue. Lead can enter water from lead service lines, lead solder (used in homes built before 1986), and brass fixtures. Even if your city's water is lead-free at the treatment plant, your home's plumbing may introduce lead. Homes built before 1986 should consider testing their water at the tap. Running cold water for 30 seconds before drinking is always a good practice.
Yes, Honolulu's water system has 3 documented EPA violations in its compliance history. All violations have been resolved, indicating the utility has taken corrective action. Violations can include exceeding contaminant limits, failure to conduct required testing, or failure to properly notify customers. Water utilities are required by the Safe Drinking Water Act to address violations and notify affected customers. You can look up the full violation history through the EPA's ECHO database or by contacting your water utility directly.
There are several options for testing your water in Honolulu. For the most comprehensive results, use a state-certified laboratory (find one at epa.gov/dwlabcert). Home test kits like Tap Score provide EPA-certified lab analysis with easy-to-understand results. Basic test strips available at hardware stores can screen for common parameters like chlorine, pH, hardness, and lead, though they are less accurate than laboratory testing. You can also request the latest testing data directly from HONOLULU WATER SYSTEM. Testing at your tap is important because it captures contamination from your household plumbing that city-level monitoring at distribution points does not detect.