Is Mililani Bws, HI Tap Water Safe to Drink?
Graded A+ — but Vanadium was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
97.5/100
waterverge.com Mililani Bws, HI — Water Quality Report
Mililani Bws's drinking water received a grade of A+ (97.5 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 50,573 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. PFAS testing under UCMR 5 found no detectable forever chemicals.
The system has 14 violations on record, including 0 health-based violations. All violations have been resolved.
What to know about Mililani Bws's water
Mililani Bws ranks #7 out of 66 cities in Hawaii for water quality, placing it one of the best in the state.
Mililani Bws relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
Hexavalent chromium (chromium-6) was detected at 1.90 µg/L in UCMR 3 testing. While below California's 10 µg/L limit and with no federal MCL set, residents sensitive to this contaminant may consider reverse osmosis filtration.
Water quality score
See methodology →Is Mililani Bws, HI water safe to drink?
Based on EPA testing data, Mililani Bws's tap water is generally safe to drink. The water system earned a grade of A+ (97.5/100), meeting federal drinking water standards across key contaminant categories. The city's 1 water system serves approximately 50,573 residents using groundwater (wells).
Recent water quality updates for Mililani Bws
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Mililani Bws's water quality assessment. Grade: A+ (97.5/100).
Federal disaster declaration (FEMA DR-3529). Hurricane event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3404). Hurricane event — may have impacted local water infrastructure.
Contaminants: Coliform (TCR).
Contaminants: Coliform (TCR).
Contaminants: Coliform (TCR).
Key contaminant findings
Based on the most recent EPA sampling data for Mililani Bws's water supply.
Well within EPA limits.
Violation history
Mililani Bws's water system has 14 total violations on record, including 0 health-based violations. All violations have been resolved.
Flood & environmental risk
Honolulu County has experienced 9 federally declared disasters since 1974. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include N. Halawa Str Nr Honolulu, Oahu, N. Halawa Str Nr Quar. Stn. At Halawa, Oahu, South Halawa Stream Nr H-3 Freeway, Oahu, Moanalua Stream Nr Kaneohe, Oahu, Kalihi Str Nr Honolulu, Oahu.
Where does Mililani Bws's water come from?
Mililani Bws's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 50,573 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include N. Halawa Str Nr Honolulu, Oahu (river), N. Halawa Str Nr Quar. Stn. At Halawa, Oahu (river), South Halawa Stream Nr H-3 Freeway, Oahu (river), Moanalua Stream Nr Kaneohe, Oahu (river), Kalihi Str Nr Honolulu, Oahu (river).
What Mililani Bws residents can do
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Mililani Bws's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Forever chemicals overview
National PFAS report →Violation summary
Violations & advisories
Flood & disaster history
Honolulu County has experienced 9 federally declared disasters since 1974. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
| 11Cl-PF3OUdS | ND | HI | µg/L | PFAS | Not Detected |
| 4:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 6:2 FTS 6:2 FTSPFAS A fluorotelomer sulfonate commonly found at sites contaminated with aqueous film-forming foam (AFFF) used in firefighting. Health EffectsPotential liver toxicity and endocrine disruption. Less studied but identified as a contaminant of concern. EPA LimitNo individual MCL (not yet regulated) Common SourcesFirefighting foam (AFFF), airports, military bases, and industrial facilities. | ND | HI | µg/L | PFAS | Not Detected |
| 8:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 9Cl-PF3ONS | ND | HI | µg/L | PFAS | Not Detected |
| ADONA | ND | HI | µg/L | PFAS | Not Detected |
| HFPO-DA HFPO-DA (GenX)PFAS A replacement for PFOA in manufacturing, marketed as safer but still a persistent "forever chemical." Also known as GenX. Health EffectsLiver and kidney effects, reproductive toxicity, immune system effects, and potential cancer risk. EPA Limit10 ppt MCL Common SourcesFluoropolymer manufacturing (used as PFOA replacement), industrial wastewater discharge. | ND | 0.01 | µg/L | PFAS | Not Detected |
| lithium LithiumInorganic A naturally occurring alkali metal found in groundwater. Monitored under UCMR 5 to assess occurrence in drinking water. Health EffectsKidney effects at high doses. Low-level exposure effects under study; some research suggests neurological effects. EPA LimitNo MCL (monitoring only under UCMR 5) Common SourcesNatural mineral deposits, geothermal water, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| NEtFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| NFDHA | ND | HI | µg/L | PFAS | Not Detected |
| NMeFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| PFBA PFBAPFAS One of the shortest-chain PFAS compounds. Very mobile in water and difficult to remove with standard filtration. Health EffectsThyroid effects, potential developmental toxicity. Shorter half-life in body than long-chain PFAS. EPA LimitNo individual MCL (not yet regulated) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and firefighting foam. | ND | HI | µg/L | PFAS | Not Detected |
| PFBS PFBSPFAS A short-chain PFAS used as a replacement for PFOS. While it clears the body faster than long-chain PFAS, it still persists in the environment. Health EffectsThyroid effects, reproductive and developmental toxicity, kidney effects. EPA LimitPart of Hazard Index (1.0) Common SourcesIndustrial discharge, firefighting foam, and as a replacement chemical in manufacturing. | ND | HI | µg/L | PFAS | Not Detected |
| PFDA | ND | HI | µg/L | PFAS | Not Detected |
| PFDoA | ND | HI | µg/L | PFAS | Not Detected |
| PFEESA | ND | HI | µg/L | PFAS | Not Detected |
| PFHpA PFHpAPFAS A medium-chain PFAS compound found in various environmental samples. Less studied than PFOA/PFOS but still considered a contaminant of concern. Health EffectsLiver effects, potential developmental toxicity, and endocrine disruption. EPA LimitPart of Hazard Index (1.0) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFHpS | ND | HI | µg/L | PFAS | Not Detected |
| PFHxA PFHxAPFAS A short-chain PFAS replacement chemical widely used after manufacturers phased out longer-chain PFAS. Very commonly detected in water. Health EffectsLiver and kidney effects, potential thyroid disruption. Considered less toxic than long-chain PFAS but still persistent. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial processes, firefighting foam (AFFF), food packaging, and textile treatment. | ND | HI | µg/L | PFAS | Not Detected |
| PFHxS PFHxSPFAS A medium-chain PFAS found in firefighting foam and consumer products. It has a long half-life in the human body, similar to long-chain PFAS. Health EffectsImmune system effects, thyroid disruption, and potential reproductive and developmental harm. EPA LimitPart of Hazard Index (1.0) Common SourcesFirefighting foam (AFFF), waterproof textiles, food packaging, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| PFMBA | ND | HI | µg/L | PFAS | Not Detected |
| PFMPA | ND | HI | µg/L | PFAS | Not Detected |
| PFNA PFNAPFAS A long-chain PFAS compound used in manufacturing fluoropolymers. It bioaccumulates in the body and is very persistent in the environment. Health EffectsDevelopmental effects, liver toxicity, immune suppression, and potential cancer risk. EPA LimitPart of Hazard Index (1.0) Common SourcesFluoropolymer manufacturing, industrial emissions, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFOA PFOAPFAS A long-chain PFAS ("forever chemical") once widely used in nonstick coatings and firefighting foam. It persists in the body and environment for years. Health EffectsLinked to kidney and testicular cancer, thyroid disease, elevated cholesterol, and reproductive issues. EPA Limit4.0 ppt MCL Common SourcesIndustrial discharge, firefighting foam (AFFF), nonstick cookware manufacturing, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFOS PFOSPFAS A long-chain PFAS compound historically used in stain-resistant coatings and firefighting foam. One of the most studied and persistent PFAS chemicals. Health EffectsLiver damage, immune system suppression, thyroid disruption, increased cholesterol, and potential cancer risk. EPA Limit4.0 ppt MCL Common SourcesFirefighting foam (AFFF), industrial sites, stain-resistant fabric treatments, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFPeA PFPeAPFAS A short-chain PFAS compound commonly detected in drinking water. One of the most frequently found PFAS in UCMR 5 monitoring. Health EffectsLess studied than PFOA/PFOS. Potential liver and thyroid effects. Research is ongoing. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial discharge, firefighting foam degradation, and consumer products. | ND | HI | µg/L | PFAS | Not Detected |
| PFPeS | ND | HI | µg/L | PFAS | Not Detected |
| PFTA | ND | HI | µg/L | PFAS | Not Detected |
| PFTrDA | ND | HI | µg/L | PFAS | Not Detected |
| PFUnA | ND | HI | µg/L | PFAS | Not Detected |
Lead level trend (90th percentile)
See how Mililani Bws compares by contaminant
Explore where Mililani Bws ranks among all Hawaii cities for specific contaminants.
Water source & infrastructure
Where Mililani Bws's water comes from
Mililani Bws's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 50,573 people through 1 water system.
Water bodies near Mililani Bws
Mililani Bws is located near 5 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Mililani Bws
| System Name | PWSID | Population | Source |
|---|---|---|---|
| MILILANI | HI0000367 | 50,573 | GW |
How Mililani Bws compares
Full Hawaii rankings →Mililani Bws's score of 97.5/100 is above the average of 90/100 among major Hawaii cities. It outscores 10 of 10 nearby cities.
Nearby cities
View Hawaii rankings →About Mililani Bws, HI
Wikipedia →Honolulu is the capital and most populous city of the U.S. state of Hawaii, located in the Pacific Ocean. It is the county seat of the consolidated City and County of Honolulu, situated along the southeast coast of the island of Oʻahu. The population of Honolulu was 350,964 at the 2020 census, dropping to an estimated 344,967 by 2024. The Urban Honolulu metropolitan area had an estimated population of just under 1 million residents in 2024 and is the 56th-largest metropolitan area in the nation.
Learn more about your water
Guides and resources related to Mililani Bws's water quality findings.
Explore water quality across Honolulu
Frequently asked questions
Is Mililani Bws, HI tap water safe to drink?
Mililani Bws's water quality earned a grade of A+ (97.5/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #7 out of 66 cities tested in Hawaii.
What contaminants are in Mililani Bws's water?
Lead was measured at 0.0 ppb (90th percentile). No PFAS compounds were detected. 14 violations are on record.
How is Mililani Bws's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Mililani Bws?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mililani Bws's water come from?
Mililani Bws's water is sourced from Groundwater. The city has 1 water system serving approximately 50,573 residents.
Is Mililani Bws's groundwater at risk of contamination?
Mililani Bws uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 14 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Mililani Bws's water compare to other cities?
Mililani Bws ranks #7 out of 66 cities in Hawaii (better than 89% of state cities) and #70 out of 15744 cities nationally (100th percentile). The grade of A+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.