Durham, CA tap water
Supplied mostly by Durham Irrigation District, plus 2 other utilities. 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
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)
0.6–25 ppm (Worth knowing)
Typical 11 ppm
Water changes can't take your tank's nitrate below this level.
From California Water Board lab results, measured before treatment; California Water Service (Cal Water) - Chico District's 2025 water quality report (2023–2026).
Copper at home taps
Up to 0.18 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; California Water Service (Cal Water) - Chico District's 2025 water quality report (2024–2025).
Chlorine or chloramine at the tap
0.6–1.1 ppm
Typical 0.6 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: California Water Service (Cal Water) - Chico District's 2025 water quality report.
Water chemistry
General hardness
80–322 ppm
Typical 124 ppm
Moderately soft to medium. Suits most community fish and plants.
From California Water Service (Cal Water) - Chico District's 2025 water quality report; California Water Board lab results, measured before treatment (2025–2026).
Carbonate hardness (alkalinity)
99–280 ppm
Typical 133 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From California Water Service (Cal Water) - Chico District's 2025 water quality report; California Water Board lab results, measured before treatment (2025–2026).
pH
6.4–8.6
Typical 7.4
Most community fish do well here. Stable water matters more than the exact number.
From EPA monitoring data, measured before treatment; California Water Service (Cal Water) - Chico District's 2025 water quality report; California Water Board lab results, measured before treatment (2017–2026).
Total dissolved solids
90–440 ppm
Typical 222 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 Service (Cal Water) - Chico District's 2025 water quality report; California Water Board lab results, measured before treatment (2025–2026).
Who supplies Durham, CA
Durham Irrigation District
Serves 33% of residents · Groundwater (wells) · Chlorine
- 2025 water quality report
California Water Service (Cal Water) - Chico District
Serves 13% of residents · Groundwater (wells) · Chlorine
Butte Creek Estates Mutual Water Co
Serves 7% 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.
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.