San Rafael, CA tap water
Supplied by Marin Municipal Water District. Here's what its 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)
Estimate0.44 ppm (Low)
This is what a conditioner frees when it breaks the chloramine apart. A cycled filter clears it within a day.
Estimated from the chloramine level Marin Municipal Water District reports (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)
1.9 ppm (Low)
Low, so water changes lower your tank's nitrate well.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
Copper at home taps (first draw)
0.16 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.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
Chlorine or chloramine at the tap
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: Marin Municipal Water District's 2025 water quality report.
Water chemistry
General hardness
47–120 ppm
Typical 59 ppm
Soft. Good for tetras, rasboras and most shrimp. Livebearers, snails and African cichlids prefer harder water.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
Carbonate hardness (alkalinity)
38–140 ppm
Typical 51 ppm
Moderate buffering. pH should stay fairly steady.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
pH
7.5–9.6
Typical 8
Most community fish do well here. Stable water matters more than the exact number.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
Total dissolved solids
109–180 ppm
Typical 128 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
Published by your utility: Marin Municipal Water District's 2025 water quality report.
- Marin Municipal Water District adds phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies San Rafael, CA
- 2025 water quality report
Marin Municipal Water District
Serves all residents · Lake or river water · 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.
Tap water lookup covers US cities only for now. Want to know why it matters? Read our story on tap water.
Compiled by Shoal & Stem from public records. Free to cite with a link.