We read 15 results from Norwalk - City, Water Dept.’s 2025 water quality report. No results over a legal limit; 6 above a health goal or guideline.
Serves about 20,283 people · Water system ID CA1910191 · 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 |
|---|---|---|---|---|
| Arsenicaverage · range ND to 9.9 · Groundwater wells · 2025 report, page 3 | 6.9 ppb | 0.004 ppb | 10 ppb | Above the health goal1,725x the health goal |
| Chromium-6average · range 0.07 to 1.6 · Groundwater wells · 2025 report, page 3 | 0.9 ppb | 0.02 ppb | 10 ppb | Above the health goal45x the health goal |
| Copper90th percentile of 30 homes tested, 0 over the action level · sampled 2022 · Customer taps · 2025 report, page 3 | 0.34 ppm | 0.3 ppm | 1.3 ppm (action level) | Above the health goal1.1x the health goal |
| Gross alpha (radioactivity)average · range ND to 2.85 · Groundwater wells · 2025 report, page 3 | 0.57 pCi/L | 0 pCi/L | 15 pCi/L | Above the health goalThe health goal is zero |
| Tetrachloroethylene (PCE)average · range ND to 1.6 · Groundwater wells · 2025 report, page 3 | 0.59 ppb | 0.06 ppb | 5 ppb | Above the health goal9.8x the health goal |
| Uraniumaverage · range 2.24 to 10.3 · printed as 3.8 pCi/L · Groundwater wells · 2025 report, page 3 | 5.66 ppb | 0.6 ppb | 30 ppb | Above the health goal9.4x the health goal |
| 1,1-Dichloroethyleneaverage · range ND to 1.7 · Groundwater wells · 2025 report, page 3 | 0.33 ppb | 7 ppb | 7 ppb | Below the health goal |
| Bariumaverage · range ND to 0.18 · Groundwater wells · 2025 report, page 3 | 0.11 ppm | 2 ppm | 2 ppm | Below the health goal |
| Chlorinehighest running annual average · range 0.11 to 2.93 · Distribution system · 2025 report, page 3 | 1.5 ppm | None set | 4 ppm | Below the legal limit |
| Disinfection byproducts (HAA5)highest running annual average · range 1 to 7.5 · Distribution system · 2025 report, page 3 | 6.4 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 3.4 to 34.6 · Distribution system · 2025 report, page 3 | 28.3 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.26 to 0.34 · Groundwater wells · 2025 report, page 3 | 0.29 ppm | 1 ppm | 2 ppm | Below the health goal |
| Lead90th percentile of 30 homes tested, 0 over the action level · sampled 2022 · Customer taps · 2025 report, page 3 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)average · range ND to 2.7 · Groundwater wells · 2025 report, page 3 | 0.6 ppm | 10 ppm | 10 ppm | Below the health goal |
| Trichloroethylene (TCE)average · range ND to 2.2 · Groundwater wells · 2025 report, page 3 | 0.98 ppb | 1.7 ppb | 5 ppb | Below the health goal |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper. 1 number we weren’t sure about is held back until a person checks.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in Norwalk - City, Water Dept.’s water between Feb 2024 and Nov 2024. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- PFOA5.2 pptFound in 4 of 20 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
- PFOS26 pptFound in 4 of 20 samples · highest resultAbove the federal limit that takes effect in 2029 (4 ppt)
- PFHxS7.6 pptFound in 4 of 20 samples · highest resultNo federal limit in force for this one
- Lithium59 ppbFound in 16 of 20 samples · highest resultAbove EPA’s health reference level of 10 ppb (a guide, not a legal limit)
Source: EPA UCMR 5 occurrence data. The highest single result is shown; one high sample doesn’t mean every glass is that high.
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.
Copper
Found: Copper
What removes it: Reverse osmosis.
Radium and uranium
Found: Gross alpha (radioactivity), Uranium
What removes it: Reverse osmosis.
Industrial chemicals and pesticides
Found: Tetrachloroethylene (PCE)
What removes it: Carbon block or RO.
PFAS ("forever chemicals")
Found: PFOA (EPA testing), PFOS (EPA testing)
What removes it: Reverse osmosis.
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