Cayucos, CA tap water
Supplied mostly by Slo Csa No. 10 - Cayucos WTP, plus 3 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)
Not detected (Low)
Not detected in testing, so water changes lower your tank's nitrate well.
From California Water Board lab results; Slo Csa No. 10 - Cayucos WTP, which supplies Slocsa #10A - Cayucos; Slo Csa No. 10 - Cayucos WTP, which supplies Cayucos Beach Mutual Water Company; Slo Csa No. 10 - Cayucos WTP, which supplies Morro Rock Mutual Water Co (2025–2026).
Copper at home taps
Up to 0.06 ppm (Low)
Typically not detected
Not detected in testing. Water that sits in household pipes overnight can still pick some up.
From California Water Board lab results (2023–2026).
Water chemistry
General hardness
266 ppm
Hard. Ideal for livebearers and African cichlids. Soft-water species may struggle to breed.
From California Water Board lab results; Slo Csa No. 10 - Cayucos WTP, which supplies Slocsa #10A - Cayucos; Slo Csa No. 10 - Cayucos WTP, which supplies Cayucos Beach Mutual Water Company; Slo Csa No. 10 - Cayucos WTP, which supplies Morro Rock Mutual Water Co (2025–2026).
Carbonate hardness (alkalinity)
218 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From California Water Board lab results; Slo Csa No. 10 - Cayucos WTP, which supplies Slocsa #10A - Cayucos; Slo Csa No. 10 - Cayucos WTP, which supplies Cayucos Beach Mutual Water Company; Slo Csa No. 10 - Cayucos WTP, which supplies Morro Rock Mutual Water Co (2025–2026).
pH
8
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From California Water Board lab results; Slo Csa No. 10 - Cayucos WTP, which supplies Slocsa #10A - Cayucos; Slo Csa No. 10 - Cayucos WTP, which supplies Cayucos Beach Mutual Water Company; Slo Csa No. 10 - Cayucos WTP, which supplies Morro Rock Mutual Water Co (2025–2026).
Total dissolved solids
385 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; Slo Csa No. 10 - Cayucos WTP, which supplies Slocsa #10A - Cayucos; Slo Csa No. 10 - Cayucos WTP, which supplies Cayucos Beach Mutual Water Company; Slo Csa No. 10 - Cayucos WTP, which supplies Morro Rock Mutual Water Co (2025–2026).
Who supplies Cayucos, CA
Slo Csa No. 10 - Cayucos WTP
Serves 54% of residents · Lake or river water · Chlorine
Slocsa #10A - Cayucos
Serves 22% of residents · Buys water from Slo Csa No. 10 - Cayucos WTP · Chlorine
Cayucos Beach Mutual Water Company
Serves 15% of residents · Buys water from Slo Csa No. 10 - Cayucos WTP · Chlorine
Morro Rock Mutual Water Co
Serves 13% of residents · Buys water from Slo Csa No. 10 - Cayucos WTP · 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.
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Compiled by Shoal & Stem from public records. Free to cite with a link.