We read 16 results from Western MWD’s 2024 water quality report. No results over a legal limit; 5 above a health goal or guideline.
Serves about 86,062 people · Water system ID CA3310049 · Read the district’s 2024 report (opens in a new tab)
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Results from the 2024 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 19 · Murrieta groundwater · 2024 report, page 10 | 2 ppb | 0.004 ppb | 10 ppb | Above the health goal500x the health goal |
| Bromatehighest running annual average · range ND to 19 · Riverside distribution, highest of 3 sources · 2024 report, page 12 | 7.9 ppb | 0.1 ppb | 10 ppb | Above the health goal79x the health goal |
| Chromium-6average · range ND to 2.1 · Riverside groundwater · 2024 report, page 10 | 1.2 ppb | 0.02 ppb | 10 ppb | Above the health goal60x the health goal |
| Perchlorateaverage · range ND to 2.9 · Riverside groundwater · 2024 report, page 10 | 1.3 ppb | 1 ppb | 6 ppb | Above the health goal1.3x the health goal |
| Total dissolved solidsaverage · range 560 to 572 · Rainbow surface water (Skinner plant), highest of 5 sources · 2024 report, page 11 | 566 ppm | — | 500 ppm guideline | Above the guideline1.1x the guideline (taste, odor or stains; not a health limit) |
| Aluminumhighest running annual average · range ND to 0.16 · printed as 74 µg/L · Rainbow surface water (Skinner plant) · 2024 report, page 10 | 0.07 ppm | — | 0.2 ppm guideline | Within the guideline |
| Bariumaverage · range ND to 0.3 · Murrieta groundwater · 2024 report, page 10 | 0.1 ppm | 2 ppm | 2 ppm | Below the health goal |
| Chloramineaverage · range 0.7 to 2.9 · Rainbow distribution, highest of 3 sources · 2024 report, page 13 | 1.97 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of 34 homes tested, 0 over the action level · Riverside customer taps, highest of 3 sources · 2024 report, page 8 | 0.26 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range 5 to 15 · Rainbow distribution, highest of 3 sources · 2024 report, page 12 | 9 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 2 to 26 · Riverside distribution, highest of 3 sources · 2024 report, page 12 | 42 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.6 to 0.9 · Riverside surface water (Mills plant), highest of 5 sources · 2024 report, page 10 | 0.7 ppm | 1 ppm | 2 ppm | Below the health goal |
| Lead90th percentile of 34 homes tested, 0 over the action level · Riverside customer taps, highest of 3 sources · 2024 report, page 8 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Nitrate (as N)average · range 2.8 to 6.8 · Riverside groundwater, highest of 3 sources · 2024 report, page 10 | 5 ppm | 10 ppm | 10 ppm | Below the health goal |
| Sulfateaverage · range 195 to 203 · Rainbow surface water (Skinner plant), highest of 5 sources · 2024 report, page 11 | 199 ppm | — | 250 ppm guideline | Within the guideline |
| Total organic carbonaverage · range 2 to 3.2 · Murrieta surface water, highest of 3 sources · 2024 report, page 10 | 2.6 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.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in Western MWD’s water between Mar 2023 and Dec 2023. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- PFHxS3.4 pptFound in 1 of 12 samples · highest resultNo federal limit in force for this one
- PFBS3 pptFound in 1 of 12 samples · highest resultNo federal limit in force for this one
- Lithium16 ppbFound in 1 of 12 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.
Industrial chemicals and pesticides
Found: Perchlorate
What removes it: Carbon block or RO.
Salty taste / high TDS
Found: Total dissolved solids
What removes it: Reverse osmosis.
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