01The verdict: is Mahanalua Nui water safe?
Based on EPA testing data, Mahanalua Nui's tap water is generally safe to drink. The water system earned a grade of A+ (97/100), meeting federal drinking water standards across key contaminant categories. The city's 1 water system serves approximately 606 residents using groundwater (wells).
Nothing over a legal limit
Every contaminant measured in Mahanalua Nui's water is within its EPA limit, and no violations are unresolved.
See the testing ↓A clean compliance record
Mahanalua Nui has no EPA violations on file — a stronger record than most systems its size.
See the record ↓A flood-prone service area
9 federal disaster declarations on record. After severe weather, watch for boil-water advisories.
See the risk factors ↓Mahanalua Nui's drinking water received a grade of A+ (97 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 606 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program. No violations are on record for this water system.
Mahanalua Nui ranks #11 out of 64 cities in Hawaii for water quality, placing it above average in the state. Mahanalua Nui 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. As a small community water system, Mahanalua Nui may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. Mahanalua Nui has a clean compliance record with no violations on file, reflecting strong operational practices.
02What's in Mahanalua Nui's water
Every contaminant flagged in Mahanalua Nui, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
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 |
Cities ranked by 90th-percentile lead PF PFAS in Hawaii
Cities ranked by compounds detected Cu Copper in Hawaii
Cities ranked by 90th-percentile copper
03Mahanalua Nui's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. No violations are on record for this water system.
All ten of the last ten years were clean — no EPA violations recorded for Mahanalua Nui.
▼ Down 5 ppb since 2010. Latest reading: 0 ppb (2021) — 0% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Mahanalua Nui's water comes from
Mahanalua Nui's drinking water is drawn from underground aquifers through wells.
Groundwater
Underground aquifers reached by wells — naturally filtered, but can carry minerals like arsenic and nitrate.
Local treatment
Groundwater generally needs less treatment — typically disinfection and, where needed, mineral removal.
1 system
1 water system, operated under private ownership.
606 people
Residents served across Mahanalua Nui's service area.
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 private ownership and serves approximately 606 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| MAHANALUA NUI SUBDIVISON | HI0000251 | 606 | Groundwater |
Water bodies near Mahanalua Nui
These water bodies shape the regional watershed and can indirectly affect groundwater quality.
05Pressure on Mahanalua Nui's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Flood & storm history
9 federal disaster declarations on record for Maui County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Mahanalua Nui compares
Scores for nearby Hawaii cities on one line, with the average marked.
dashed line = Hawaii average (92/100)
Mahanalua Nui scores 97/100 — on par with the Hawaii average of 92/100. It outscores 9 of 10 nearby cities. Full Hawaii rankings →
91.1 / 100AWaipahu-Ewa-Waianae, HI
92.8 / 100AWailuku, HI
91.4 / 100APearl Harbor, HI
94.8 / 100AMililani Bws, HI
97.5 / 100ASchofield Barracks, HI
91.8 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Mahanalua Nui's water — not generic advice.
A basic carbon filter still helps
Mahanalua Nui's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Mahanalua Nui alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Mahanalua Nui, HI tap water safe to drink?
Mahanalua Nui's water quality earned a grade of A+ (97/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #11 out of 64 cities tested in Hawaii.
What contaminants are in Mahanalua Nui's water?
Lead was measured at 0.0 ppb (90th percentile). No violations on record.
How is Mahanalua Nui'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 Mahanalua Nui?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mahanalua Nui's water come from?
Mahanalua Nui's water is sourced from Groundwater. The city has 1 water system serving approximately 606 residents.
Is Mahanalua Nui's groundwater at risk of contamination?
Mahanalua Nui uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. Current testing shows the groundwater meets EPA standards. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Mahanalua Nui's water compare to other cities?
Mahanalua Nui ranks #11 out of 64 cities in Hawaii (better than 83% of state cities) and #116 out of 15382 cities nationally (99th percentile). The grade of A+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Mahanalua Nui's small water system affect quality?
Mahanalua Nui's system serves approximately 606 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has maintained a clean compliance record.