Angwin, CA tap water
Supplied mostly by Howell Mountain Mutual Water Company, plus 1 other utility. Here's what the water means for your fish.
Disinfectant
Chlorine
Your water is treated with chlorine. It slowly gases off from standing water, and any water conditioner removes it.
Safety for fish and shrimp
Nitrate (NO₃)
Up to 11 ppm (Low)
Typically not detected
Not detected in testing, so water changes lower your tank's nitrate well.
From California Water Board lab results, measured before treatment (2023–2026).
Copper at home taps
Up to 0.05 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 (2023–2024).
Water chemistry
General hardness
20–43 ppm
Typical 24 ppm
Soft. Good for tetras, rasboras and most shrimp. Livebearers, snails and African cichlids prefer harder water.
From California Water Board lab results, measured before treatment (2023–2026).
Carbonate hardness (alkalinity)
28–57 ppm
Typical 30 ppm
Little buffering. pH can drop quickly between water changes, especially with CO₂ or an older tank.
From California Water Board lab results, measured before treatment (2023–2026).
pH
6.1–6.9
Typical 6.9
Most community fish do well here. Stable water matters more than the exact number.
From California Water Board lab results, measured before treatment (2023–2026).
Total dissolved solids
60–160 ppm
Typical 96 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, measured before treatment (2023–2026).
- Howell Mountain Mutual Water Company adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies Angwin, CA
Howell Mountain Mutual Water Company
Serves 51% of residents · Lake or river water · Chlorine
Pacific Union College
Serves 37% of residents · Groundwater (wells) · Chlorine
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.