Clearlake, CA tap water
Supplied mostly by Highlands Mutual Water Company, 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 (2025–2026).
Nitrate (NO₃)
Up to 2.9 ppm (Low)
Typically not detected
Not detected in testing, so water changes lower your tank's nitrate well.
From California Water Board lab results; EPA monitoring data (2017–2026).
Copper at home taps
0.11–0.26 ppm (Worth knowing)
Typical 0.14 ppm
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 California Water Board lab results (2023–2026).
Water chemistry
General hardness
130–150 ppm
Typical 140 ppm
Moderately soft to medium. Suits most community fish and plants.
From California Water Board lab results (2023–2026).
Carbonate hardness (alkalinity)
140–160 ppm
Typical 140 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From California Water Board lab results (2023–2026).
pH
7.5–7.9
Typical 7.7
Most community fish do well here. Stable water matters more than the exact number.
From California Water Board lab results; EPA monitoring data (2017–2026).
Total dissolved solids
180–200 ppm
Typical 200 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 (2023–2026).
- Konocti County Water District and Golden State Water Co.-Clearlake System add phosphate to protect pipes. It can feed algae in tanks without much plant growth.
Who supplies Clearlake, CA
Highlands Mutual Water Company
Serves 42% of residents · Lake or river water · Chlorine
Konocti County Water District
Serves 29% of residents · Lake or river water · Chlorine
Golden State Water Co.-Clearlake System
Serves 29% of residents · Lake or river water · 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.