Martinez, CA tap water
Supplied mostly by Contra Costa 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 about 0.44 ppm of ammonia here. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Ammonia (with conditioner)
EstimateUp to 1.58 ppm (Worth knowing)
Typical 1.17 ppm
About 0.73 ppm is already in the water, and a conditioner frees about 0.44 ppm more when it breaks the chloramine apart. 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. Some conditioners also bind ammonia for a day or so.
Estimated from the chloramine level Contra Costa Water District reports; Contra Costa Water District's 2025 water quality report; California Water Board lab results (2024–2025).
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 1.3 ppm
Low, so water changes lower your tank's nitrate well.
From Contra Costa Water District's 2025 water quality report; California Water Board lab results (2023–2026).
Copper at home taps (first draw)
0.06–0.11 ppm (Worth knowing)
The 90th percentile of first-draw samples from homes: water that sat in household pipes for at least six hours.
Shrimp and snails are sensitive to copper. Water that sits in household pipes picks up the most; it drops once the tap has run for a minute.
From Contra Costa Water District's 2025 water quality report; California Water Board lab results (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 your utility: Contra Costa Water District's 2025 water quality report.
Water chemistry
General hardness
53–116 ppm
Typical 74 ppm
Moderately soft to medium. Suits most community fish and plants.
From Contra Costa Water District's 2025 water quality report; California Water Board lab results (2023–2025).
Carbonate hardness (alkalinity)
44–82 ppm
Typical 53 ppm
Moderate buffering. pH should stay fairly steady.
From Contra Costa Water District's 2025 water quality report; California Water Board lab results (2023–2026).
pH
7.9–9
Typical 8.5
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From Contra Costa Water District's 2025 water quality report; California Water Board lab results (2023–2026).
Total dissolved solids
120–303 ppm
Typical 210 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 Contra Costa Water District's 2025 water quality report; California Water Board lab results (2023–2026).
Who supplies Martinez, CA
- 2025 water quality report
Contra Costa Water District
Serves 65% of residents · Lake or river water · Chloramine
City of Martinez
Serves 36% of residents · Buys water from Contra Costa 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.