CALIFORNIA WATER SERVICE-S SAN FRANCISCO Water Quality Report
Serving roughly 64,146 people in San Mateo County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for CALIFORNIA WATER SERVICE-S SAN FRANCISCO
1 water provider directly on file, serving roughly 64,146 people in San Mateo County, California.
Quick answer: CALIFORNIA WATER SERVICE-S SAN FRANCISCO has no violations on file. One reading is worth knowing about: Magnesium was measured at 43MG/L, among the highest of the 113 providers on file in this area. It's the most notable figure in this system's record among its 113 local peers.
Lead Summary
Lithium
Magnesium
Potassium
Sodium
Calcium
Orthophosphate
Fluoride
Nitrate
Boron, Total
Vanadium, Total
Manganese
Totalhaloaceticacids (HAA5)
TTHM
1, 2, 3-Trichloropropane
Iron
Chromium, Hex
Utility CALIFORNIA WATER SERVICE-S SAN FRANCISCOPopulation served 64,146Owner Private
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.0041 mg/L (ppm)
12/31/2025
Vanadium, Total
Detected: 2.7 UG/L (ppb)
9/9/2025
Manganese
Detected: 4.9 UG/L (ppb)
9/9/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Iron
Detected: 131 UG/L (ppb)
9/9/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Chromium, Hex
Detected: 0.45 UG/L (ppb)
8/12/2025
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 41 UG/L (ppb)
9/10/2025
TTHM
Detected: 50 UG/L (ppb)
9/10/2025
A group of disinfection byproducts formed when chlorine reacts with organic matter. Long-term exposure above the legal limit has been linked to increased cancer risk in some studies.
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Fluoride
Detected: 0.1 MG/L (ppm)
8/25/2025
Often added deliberately for dental health; can also occur naturally.
Nitrate
Detected: 1.3 MG/L (ppm)
9/29/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Boron, Total
Detected: 64 UG/L (ppb)
9/9/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 43 MG/L (ppm)
9/9/2025
Potassium
Detected: 4 MG/L (ppm)
9/9/2025
Sodium
Detected: 89 MG/L (ppm)
9/9/2025
Calcium
Detected: 84 MG/L (ppm)
9/9/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Orthophosphate
Detected: 0.6 MG/L (ppm)
9/29/2025
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
Lithium
Detected: 23.6 µg/L (ppb)
2/5/2025
Occurs naturally in some groundwater. Not currently federally regulated in drinking water.
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
1, 2, 3-Trichloropropane
Detected: 0.006 UG/L (ppb)
9/11/2025
Filtration considerations: See the table below for how whole-house carbon, under-sink reverse osmosis, and under-sink carbon systems compare against what's actually on file here. These are general system types, not a specific product recommendation.