Mountain View, CA tap water
Supplied mostly by City of Mountain View, 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
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)
Supplier's figureUp to 32 ppm (Low)
Typical 0.8 ppm
Low, so water changes lower your tank's nitrate well.
From the utility that supplies yours: San Francisco Regional Water System and Santa Clara Valley Water District, which supplies City of Mountain View; 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
Supplier's figure8–106 ppm
Typical 86 ppm
Moderately soft to medium. Suits most community fish and plants.
From the utility that supplies yours: San Francisco Regional Water System and Santa Clara Valley Water District, which supplies City of Mountain View; California Water Board lab results; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2023–2026).
Carbonate hardness (alkalinity)
Supplier's figure8–102 ppm
Typical 76 ppm
Moderate buffering. pH should stay fairly steady.
From the utility that supplies yours: San Francisco Regional Water System and Santa Clara Valley Water District, which supplies City of Mountain View; California Water Board lab results; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2023–2026).
pH
Supplier's figure7.4–9
Typical 8
Most community fish do well here. Stable water matters more than the exact number.
From the utility that supplies yours: San Francisco Regional Water System and Santa Clara Valley Water District, which supplies City of Mountain View; California Water Board lab results; EPA monitoring data (2012–2026).
Total dissolved solids
Supplier's figure24–279 ppm
Typical 212 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 the utility that supplies yours: San Francisco Regional Water System and Santa Clara Valley Water District, which supplies City of Mountain View; California Water Board lab results; Santa Clara Valley Water District, which supplies Cwsc Los Altos Suburban (2023–2026).
- City of Mountain View, 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 Mountain View, CA
City of Mountain View
Serves 93% of residents · Buys water from San Francisco Regional Water System · Chloramine
Santa Clara Valley Water District
Serves 47% of residents · Lake or river water · Chloramine
Cwsc Los Altos Suburban
Serves 12% 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.