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4 cities ranked best to worst by EPA-record water quality score
Hilo has the best tap water grade in Hawaii (A, 100/100); Waipahu is lowest (A, 98/100). Overall, none of the 4 Hawaii systems we grade has a health-based EPA violation in the last five years, so the state's tap water is safe by EPA compliance records — 100% earn a B or better.
This page ranks the 4 Hawaii cities whose water systems we have matched to EPA records. Every city starts at 100 points and loses points for health-based EPA violations in the last five years (SDWIS 2026Q2), its most recent Lead and Copper Rule 90th-percentile result, PFAS detected in EPA's 2023–2026 UCMR5 monitoring, and 2012–2019 compliance samples that averaged near or above a limit. Letters follow fixed bands (A ≥90, B ≥80, C ≥70, D ≥60, F below 60). Cities run from the highest score (Hilo) down to the lowest (Waipahu); ties are ordered by population served. See the full scoring methodology for every deduction and the data vintages. 11 further Hawaii cities are listed at the bottom without a grade because we have not yet matched them to an EPA water system.
An A or B grade points to water that consistently tests within federal safety limits, while a C suggests moderate issues worth watching and a D or F flags contaminants or compliance problems serious enough to act on. These grades describe system-level water leaving the treatment plant — they can't account for your home's own plumbing, so older houses with lead service lines or fixtures can add contaminants after the water arrives. For a contaminant-by-contaminant view, see the Hawaii contaminant breakdown or drill into the county-level rankings.
What the EPA service line inventory and our Hawaii guide say, beyond the scores.
We track 15 cities in Hawaii. 4 of them are matched to an active EPA-registered community water system (PWSID). Those 4 systems report serving 911,693 people in EPA's Safe Drinking Water Information System (SDWIS).
Of 4 cities of the 15 Hawaii cities we can grade from EPA records, 4 cities (100%) grade B or better, 0 sit in the C range and 0 grade D or F. The average score is 99/100. 11 cities are not graded because they have not been matched to an EPA system yet.
None of the 4 graded systems has a health-based EPA violation in the last five years; the 0 violations on file in that window are monitoring or reporting lapses.
1 city has a Lead and Copper Rule 90th-percentile result from 2020 or later: none at 5 ppb or more — every reported result is well below the action level.
EPA's UCMR5 PFAS monitoring (2023–2026) covers 4 cities: PFAS were detected in 2 cities, all below the 4 ppt PFOA/PFOS limit.
Hilo scores highest (100) and Waipahu lowest (98), a 2-point spread.
Lead pipes are the part of tap-water risk a treatment-plant grade cannot see, so start with EPA's service line inventory (Q2 2026 snapshot). 132 Hawaii systems inventoried 336,704 service lines: 0 confirmed lead plus 529 galvanized lines requiring replacement, spread across 0 systems. Another 34,251 lines (10%) are still of unknown material, which EPA counts as possible lead until verified.
Of the 4 city-linked Hawaii utilities with an inventory on file, 4 report no lead with most lines verified. The largest, HNL-WINDWARD-PEARL HARBOR (Honolulu, 631,389 served), reports no lead lines and 100% of lines verified non-lead.
Service line counts: EPA SDWIS Service Line Inventory, Q2 2026 snapshot (updated 2026-08-18). Limits: EPA National Primary Drinking Water Regulations.
How Hawaii's 4 cities are distributed by water quality grade
4 out of 4 cities meet or exceed a B grade for water quality
Sorted by water quality score from best to worst. Click any city for a detailed water quality report.
Sources: EPA SDWIS/ECHO violations and Lead and Copper Rule results (2026Q2 extract), UCMR5 PFAS occurrence (2023–2026), SYR4 compliance samples (2012–2019). Rubric v2 — methodology.
Found your city above? These guides turn its grade into an action plan.
Pitcher vs. under-sink vs. reverse osmosis, matched to the contaminants reported in Hawaii systems.
Taste, odor, trihalomethanes, and why a carbon filter handles them
Where it comes from, how to test, and which filters are NSF 53 certified to remove it
Best filters for lead →EPA's inventory of lead pipes by water system — a risk these plant-level grades cannot capture.
Put a Hawaii city next to where you're moving from (or to) and see every contaminant head to head.
The best water quality in Hawaii is found in Hilo with a score of 100/100 and a grade of A. This puts Hilo among the top-performing cities in the country for drinking water safety.
The most concerning water quality is in Waipahu scoring 98/100 with a grade of A. Residents may want to consider home water testing and filtration options.
The statewide average score is 99/100, which is 11 points above the national average of 88/100. A strong majority (100%) of Hawaii cities exceed the national average, indicating generally good water infrastructure across the state.
Hawaii tap water averages 99/100. Even with solid scores, a certified filter removes trace contaminants and improves taste — especially useful for households with young children or anyone sensitive to chlorine or lead.
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Hilo has the best water quality grade among the 4 Hawaii cities we can grade, with a score of 100/100 (grade A). Scores start at 100 and lose points for health-based EPA violations, lead 90th-percentile results, PFAS detections in EPA's UCMR5 monitoring and historical (2012–2019) readings near a limit. 2 cities share this top score; the largest system is listed first.
It varies by utility. Across the 4 Hawaii cities we grade from EPA records, the average score is 99/100 and 100% earn a B or better. None has a health-based EPA violation in the last five years. No city grades below C. Lead from household plumbing is not captured by any city-level grade.
By population served: Honolulu grades A (98/100, #3 of 4); Waipahu grades A (98/100, #4 of 4); Hilo grades A (100/100, #1 of 4); Wahiawa grades A (100/100, #2 of 4). Each city report lists the utility's violations, lead 90th-percentile result and PFAS results.
Of the 4 graded Hawaii cities, 0 cities have a D or F grade. 4 of 4 (100%) score above the national average of 88/100 across all graded U.S. cities in our dataset. 11 further Hawaii cities are not graded because we have not matched them to an EPA water system yet.
This page ranks 4 Hawaii cities from EPA's Safe Drinking Water Information System (violations and lead results, 2026Q2), UCMR5 PFAS monitoring (2023–2026) and Six-Year Review sample data (2012–2019). Each city link opens a report with the utility's violation history, lead 90th-percentile results and PFAS table. For official Consumer Confidence Reports (CCR), contact your local water utility — federal law requires all community water systems to deliver an annual CCR to customers. The Hawaii state environmental agency and the EPA's Safe Drinking Water Information System (SDWIS) also publish official water quality data.
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Side-by-side water quality comparison
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