Oakley, CA tap water
Part of Oakley is supplied by Diablo Water District, plus 1 other utility. Here's what its water means for your fish.
Disinfectant
Chloramine
Utility water here 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
Ammonia
0.4–1.58 ppm (Worth knowing)
Typical 0.52 ppm
Ammonia in the water as delivered. A cycled filter clears it within a day; a big water change in a new or very small tank adds more of it at once.
From California Water Board lab results; the chloramine level Contra Costa Water District reports; Contra Costa Water District's 2025 water quality report (2023–2025).
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 (2023–2026).
Nitrate (NO₃)
Up to 3.5 ppm (Low)
Typical 1.2 ppm
Low, so water changes lower your tank's nitrate well.
From California Water Board lab results; Contra Costa Water District's 2025 water quality report (2023–2026).
Copper at home taps
Up to 0.11 ppm (Low)
Typical 0.01 ppm
Low. Water that sits in household pipes overnight can carry more than this.
From California Water Board lab results; Contra Costa Water District's 2025 water quality report (2023–2025).
Chlorine or chloramine at the tap
0–3.5 ppm
Typical 1.8 ppm
At tap levels, chlorine and chloramine are toxic to fish, shrimp and the bacteria in a filter. Water conditioners are made for this range.
Published by the utility: Contra Costa Water District's 2025 water quality report.
Water chemistry
General hardness
53–128 ppm
Typical 128 ppm
Moderately soft to medium. Suits most community fish and plants.
From California Water Board lab results; Contra Costa Water District's 2025 water quality report (2023–2025).
Carbonate hardness (alkalinity)
44–82 ppm
Typical 71 ppm
Moderate buffering. pH should stay fairly steady.
From California Water Board lab results; Contra Costa Water District's 2025 water quality report (2023–2025).
pH
7.9–9
Typical 8.3
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From California Water Board lab results; Contra Costa Water District's 2025 water quality report (2023–2025).
Total dissolved solids
128–303 ppm
Typical 224 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; Contra Costa Water District's 2025 water quality report (2023–2025).
Who supplies Oakley, CA
Diablo Water District
Serves 48% of residents · Buys water from Randall-Bold Water Treatment Plant · Chloramine
- 2025 water quality report
Contra Costa Water District
Serves 47% of residents · Lake or river water · Chloramine
We couldn't fully map which utility serves Oakley. These numbers come from the utilities we matched, which serve about 48% of residents.
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.