Mililani Water System water quality
Honolulu, HI · serves 50,573 people (11,915 connections) · Groundwater · Local government · EPA ID HI0000367
Data: U.S. EPA · How we read the data · How we check it
Summary
No limits exceeded in the data EPA has, but the record is incomplete: no lead results since 2018.
- PFAS
- Not detectedNone of 29 PFAS found above EPA's reporting limits in 6 samples (2023–2025).
- Lead
- Out of dateEPA's national database has no lead results for this system since 2018 (then 0 ppb, 90th percentile). Systems this size normally test every one to three years, so this most likely means newer results were not reported to EPA, not that testing stopped. Ask the utility for its latest results.
- Violations
- None health-basedNo health-based violations since 2016.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Mililani Water System's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (808) 748-5080. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 3 entry points tested Mar 2023 to Sep 2023. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Not detected Guideline 6,000 ppt | – |
| PFHxA Not detected Guideline 3,000 ppt | – |
29 PFAS tested, 0 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Not detected in 6 samples (reporting limit 9 ppb). About lithium.
Lead and copper
Latest 90th percentile: 0 ppb lead (Jan 2016 – Dec 2018). No results since 2018
This is the newest lead result in EPA's national database. Utilities report lead results to their state, and states pass them to EPA. Gaps like this usually mean the newer results did not reach EPA's database, not that the utility stopped testing. Results this old may not reflect the water today. Ask the utility or your state drinking water program for the latest lead monitoring.
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2016 – Dec 2018 | 0 ppb |
| Jan 2013 – Dec 2015 | 1 ppb |
| Jan 2010 – Dec 2012 | 0.63 ppb |
Earlier results (5)
| Jan 2007 – Dec 2009 | 1.9 ppb |
| Jan 2004 – Dec 2006 | 1.1 ppb |
| Jan 2001 – Dec 2003 | 0 ppb |
| Jan 1998 – Dec 2000 | 0 ppb |
| Jul 1992 – Dec 1992 | 2.5 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 2.4 ppb | 300 ppb |
| Vanadium | 46 ppb | 21 ppb |
| Chlorate | 46 ppb | 210 ppb |
| Chromium-6 | 1.9 ppb | – |
| Strontium | 0.061 ppm | 1.5 ppm |
| 1,2,3-Trichloropropane (TCP) | 0.057 ppb | 0.0004 ppb |
Where it serves
ZIP codes the system reported serving: 96789, 96843
Questions
Is Mililani Water System water safe to drink?
Mililani Water System has no health-based violations since 2016. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Mililani Water System water have PFAS?
EPA tested Mililani Water System for 29 PFAS between Mar 2023 and Sep 2023 and none were detected above the reporting limits (about 2 to 20 ppt depending on the chemical).
What is the lead level in Mililani Water System water?
The most recent 90th-percentile lead result for Mililani Water System is 0 ppb, for the period ending Dec 2018, which is more than five years old. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for HI0000367: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID HI0000367).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Mililani Water System at (808) 748-5080, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.