Los Altos, CA tap water
Supplied mostly by Santa Clara Valley Water District, plus 1 other utility. 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
Nitrite (NO₂)
Not detected (Low)
Not detected in testing, so any nitrite in your tank comes from the tank itself.
From California Water Board lab results; EPA monitoring data (2016–2026).
Nitrate (NO₃)
1.5–32 ppm (Low)
Typical 1.5 ppm
Low, so water changes lower your tank's nitrate well.
From California Water Board lab results; EPA monitoring data (2013–2026).
Copper at home taps
Up to 0.15 ppm (Low)
Typically not detected
Not detected in testing. Water that sits in household pipes overnight can still pick some up.
From California Water Board lab results (2025–2026).
Water chemistry
General hardness
102 ppm
Moderately soft to medium. Suits most community fish and plants.
From California Water Board lab results; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2025–2026).
Carbonate hardness (alkalinity)
68 ppm
Moderate buffering. pH should stay fairly steady.
From California Water Board lab results; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2025–2026).
pH
7.4–7.8
Typical 7.6
Most community fish do well here. Stable water matters more than the exact number.
From California Water Board lab results; EPA monitoring data (2012–2026).
Total dissolved solids
279 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; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2025–2026).
- Santa Clara Valley Water District and Cwsc Los Altos Suburban add phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies Los Altos, CA
Santa Clara Valley Water District
Serves 51% of residents · Lake or river water · Chloramine
Cwsc Los Altos Suburban
Serves 51% of residents · Buys water from Santa Clara Valley Water District · 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.