Mission Viejo, CA tap water
Supplied mostly by Santa Margarita Water District, plus 2 other utilities. Here's what the water means for your fish.
Disinfectant
Chloramine
Your water is treated with chloramine. Unlike chlorine, it doesn't gas off when water sits out, and many pitcher and fridge filters aren't rated to remove it. Conditioners that list chloramine on the label break it apart, which frees a little ammonia. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Nitrate (NO₃)
Supplier's figureUp to 14 ppm (Low)
Typical 1.2 ppm
Low, so water changes lower your tank's nitrate well.
From the utility that supplies yours: Metropolitan Water Dist. of So. Cal. and Trabuco Canyon Water District and Irvine Ranch Water District, which supplies Santa Margarita Water District; California Water Board lab results; Metropolitan Water Dist. of So. Cal. and Moulton Niguel Water District, which supplies El Toro Water District (2023–2026).
Copper at home taps (first draw)
0.03–0.08 ppm (Low)
The 90th percentile of first-draw samples from homes: water that sat in household pipes for at least six hours.
Low. Water that sits in household pipes overnight can carry more than this.
From Santa Margarita Water District's 2024 water quality report; California Water Board lab results (2023–2024).
Water chemistry
General hardness
82–313 ppm
Typical 270 ppm
Hard. Ideal for livebearers and African cichlids. Soft-water species may struggle to breed.
From Santa Margarita Water District's 2024 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Moulton Niguel Water District; Metropolitan Water Dist. of So. Cal., which supplies El Toro Water District (2023–2026).
Carbonate hardness (alkalinity)
68–144 ppm
Typical 114 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From Santa Margarita Water District's 2024 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Moulton Niguel Water District; Metropolitan Water Dist. of So. Cal., which supplies El Toro Water District (2023–2026).
pH
7–8.7
Typical 8
Most community fish do well here. Stable water matters more than the exact number.
From Santa Margarita Water District's 2024 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Moulton Niguel Water District; Metropolitan Water Dist. of So. Cal., which supplies El Toro Water District (2023–2026).
Total dissolved solids
214–712 ppm
Typical 621 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
From Santa Margarita Water District's 2024 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Moulton Niguel Water District; Metropolitan Water Dist. of So. Cal., which supplies El Toro Water District (2023–2026).
Who supplies Mission Viejo, CA
- 2024 water quality report
Santa Margarita Water District
Serves 52% of residents · Buys water from Metropolitan Water Dist. of So. Cal. · Chloramine
Moulton Niguel Water District
Serves 27% of residents · Buys water from Joint Regional Water Supply System · Chloramine
El Toro Water District
Serves 7% of residents · Buys water from Metropolitan Water Dist. of So. Cal. · Chloramine
Our data comes from public records and is still incomplete. Many utilities don't publish every number, so we're adding more all the time. Your city's range is a starting point: testing your own tap is the only way to know exactly what's in it.
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Compiled by Shoal & Stem from public records. Free to cite with a link.