Hawthorne, CA tap water
Supplied mostly by Golden State Water Company (GSWC), 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 0.58 ppm of ammonia here. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Ammonia (with conditioner)
Estimate0.02–1.64 ppm (Worth knowing)
Typical 0.58 ppm
This is what a conditioner frees 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 Golden State Water Company (GSWC) reports; 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 (2024–2026).
Nitrate (NO₃)
Supplier's figureUp to 2.9 ppm (Low)
Typically not detected
Not detected in testing, so water changes lower your tank's nitrate well.
From the utility that supplies yours: Metropolitan Water Dist. of So. Cal., which supplies Golden State Water Company (GSWC); California Water Board lab results (2023–2026).
Copper at home taps (first draw)
0.02–0.12 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 Golden State Water Company (GSWC)'s 2025 water quality report; California Water Board lab results (2023–2025).
Chlorine or chloramine at the tap
0.1–4.5 ppm
Typical 2.4 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: Golden State Water Company (GSWC)'s 2025 water quality report.
Water chemistry
General hardness
137–280 ppm
Typical 190 ppm
Moderately hard. Great for livebearers, and most community fish adapt.
From Golden State Water Company (GSWC)'s 2025 water quality report; Hawthorne-City Water Dept.'s calcium and magnesium readings (2024–2025).
Carbonate hardness (alkalinity)
68–180 ppm
Typical 150 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From Golden State Water Company (GSWC)'s 2025 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Hawthorne-City Water Dept. (2023–2026).
pH
7.8–8.4
Typical 8.2
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From Golden State Water Company (GSWC)'s 2025 water quality report; California Water Board lab results (2023–2026).
Total dissolved solids
214–666 ppm
Typical 386 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 Golden State Water Company (GSWC)'s 2025 water quality report; Metropolitan Water Dist. of So. Cal., which supplies Hawthorne-City Water Dept. (2023–2026).
Who supplies Hawthorne, CA
- 2025 water quality report
Golden State Water Company (GSWC)
Serves 54% of residents · Buys water from Metropolitan Water Dist. of So. Cal. · Chloramine
Hawthorne-City Water Dept.
Serves 46% of residents · Buys water from Metropolitan Water Dist. of So. Cal. · 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.