We read 10 results from Wailuku’s 2025 water quality report. No results over a legal limit; 2 above a health goal or guideline.
Serves about 74,511 people · Water system ID HI0000212 · Read the district’s 2025 report (opens in a new tab)
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Results from the 2025 report
Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.
| Contaminant | Result | Health goal | Legal limit | What it means |
|---|---|---|---|---|
| Gross alpha (radioactivity)highest measured · range ND to 4.5 · sampled 2020 · Sources · 2025 report, page 18 | 4.5 pCi/L | 0 pCi/L | 15 pCi/L | Above the health goalThe health goal is zero |
| Gross beta (radioactivity)highest measured · range ND to 4.7 · sampled 2020 · Sources · 2025 report, page 18 | 4.7 pCi/L | 0 pCi/L | 50 pCi/L | Above the health goalThe health goal is zero |
| Copper90th percentile of homes tested, 0 over the action level · sampled 2024 · Customer taps · 2025 report, page 19 | 0.1 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range ND to 12 · Distribution system · 2025 report, page 18 | 12 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 5.4 to 46 · Distribution system · 2025 report, page 18 | 46 ppb | None set | 80 ppb | Below the legal limit |
| Fluoridehighest measured · range ND to 0.2 · Sources · 2025 report, page 18 | 0.2 ppm | 1 ppm | 4 ppm | Below the health goal |
| Lead90th percentile of homes tested, 0 over the action level · sampled 2024 · Customer taps · 2025 report, page 19 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)highest measured · range ND to 2.5 · Sources · 2025 report, page 18 | 2.5 ppm | 10 ppm | 10 ppm | Below the health goal |
| Sulfatehighest measured · range 2.9 to 26 · Sources · 2025 report, page 20 | 26 ppm | — | 250 ppm guideline | Within the guideline |
| Sodiumhighest measured · Sources · 2025 report, page 20 | 9.4 ppm | None set | None | No health limit |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper.
What you can do
Nothing here is an emergency notice: if the district has a violation, it must tell customers directly. If you’d like to lower these at your tap, these are the treatments that remove them, and the catalog shows the models certified for each. Ranking is by certified removal; commissions never change the order.
Radium and uranium
Found: Gross alpha (radioactivity), Gross beta (radioactivity)
What removes it: Reverse osmosis.
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