San Juan Capistrano, CA tap water
Supplied by Santa Margarita Water District-ID9. Here's what its 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 2.9 ppm (Low)
Typically not detected
Not detected in testing, so water changes lower your tank's nitrate well.
From the utility that supplies yours: Metropolitan Water Dist. of So. Cal. and Smwd - Sj Ground Water Plant, which supplies Santa Margarita Water District-ID9 (2023–2026).
Copper at home taps
Not detected (Low)
Not detected in testing. Water that sits in household pipes overnight can still pick some up.
From California Water Board lab results (2024).
Water chemistry
General hardness
105–275 ppm
Typical 268 ppm
Hard. Ideal for livebearers and African cichlids. Soft-water species may struggle to breed.
From California Water Board lab results (2025).
Carbonate hardness (alkalinity)
70–120 ppm
Typical 120 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From California Water Board lab results (2025).
pH
7.3–8
Typical 7.7
Most community fish do well here. Stable water matters more than the exact number.
From EPA monitoring data (2013–2019).
Total dissolved solids
290–640 ppm
Typical 618 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 California Water Board lab results (2025).
- Santa Margarita Water District-ID9 adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies San Juan Capistrano, CA
Santa Margarita Water District-ID9
Serves all 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.