Serving roughly 7,303 people in Sonoma County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for COTATI, CITY OF
1 water provider directly on file, serving roughly 7,303 people in Sonoma County, California.
Quick answer: COTATI, CITY OF has no violations on file and no single reading stands out against its peers (756 other providers in this area). It serves roughly 7,303 people, and the full breakdown below reflects everything EPA and California have on record for it.
Lead Summary
Copper Summary
Lithium
Alkalinity, Total
pH
TTHM
Bromoform
Chloroform
Bromodichloromethane
Dibromochloromethane
Dibromoaceticacid
Dichloroaceticacid
Iron
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
Magnesium
Sodium
Calcium
TDS
Chloride
Sulfate
Turbidity
Manganese
Arsenic
Conductivity (at 25°C)
Utility COTATI, CITY OFPopulation served 7,303Owner Local government
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0 mg/L (ppm)
12/31/2023
Copper Summary
Detected: 1.6 mg/L (ppm)
12/31/1993
Iron
Detected: 1200 UG/L (ppb)
10/2/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Manganese
Detected: 240 UG/L (ppb)
10/2/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Arsenic
Detected: 2.1 UG/L (ppb)
4/15/2025
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
TTHM
Detected: 3.3 UG/L (ppb)
8/28/2025
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.
Bromoform
Detected: 3.3 UG/L (ppb)
8/28/2025
Chloroform
Detected: 1.8 UG/L (ppb)
8/28/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromodichloromethane
Detected: 2 UG/L (ppb)
8/28/2025
Dibromochloromethane
Detected: 2.5 UG/L (ppb)
8/28/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 38 MG/L (ppm)
4/15/2025
Sulfate
Detected: 20 MG/L (ppm)
4/15/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 10 MG/L (ppm)
4/15/2025
Sodium
Detected: 37 MG/L (ppm)
4/15/2025
Calcium
Detected: 20 MG/L (ppm)
4/15/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
pH
Detected: 7.8 PH
7/31/2025
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
Hardness, Total (ASCACO3)
Detected: 91 MG/L (ppm)
4/15/2025
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
Lithium
Detected: 14 µg/L (ppb)
9/9/2024
Occurs naturally in some groundwater. Not currently federally regulated in drinking water.
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 110 MG/L (ppm)
4/15/2025
Other
Additional substances tested that don't fit neatly into the categories above
Alkalinity, Total
Detected: 120 MG/L (ppm)
7/31/2025
Dibromoaceticacid
Detected: 1.1 UG/L (ppb)
8/28/2025
Dichloroaceticacid
Detected: 1.1 UG/L (ppb)
8/28/2025
TDS
Detected: 250 MG/L (ppm)
4/15/2025
Turbidity
Detected: 0.2 NTU
4/15/2025
A measure of water cloudiness from suspended particles.
Conductivity (at 25°C)
Detected: 330 UMHO/CM
4/15/2025
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.