Serving roughly 84,804 people in Napa County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
🏠Local Expertise
Results for NAPA, CITY OF
1 water provider directly on file, serving roughly 84,804 people in Napa County, California.
Quick answer: NAPA, CITY OF has no violations on file. One reading is worth knowing about: TTHM was measured at 78UG/L, among the highest of the 358 providers on file in this area. It's the most notable figure in this system's record among its 358 local peers.
Lead Summary
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Bromodichloromethane
Dibromochloromethane
Dichloroaceticacid
Trichloroaceticacid
Dibromoaceticacid
Monochloroaceticacid
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
Carbon, Total
Silica
Magnesium
Calcium
Potassium
Sodium
Chlorinedioxide
TDS
Chloride
Sulfate
Bromide
Utility NAPA, CITY OFPopulation served 84,804Owner Local government
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0 mg/L (ppm)
12/31/2024
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 29 UG/L (ppb)
7/9/2025
TTHM
Detected: 78 UG/L (ppb)
10/1/2025
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.
Chloroform
Detected: 60 UG/L (ppb)
10/1/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromodichloromethane
Detected: 15 UG/L (ppb)
10/1/2025
Dibromochloromethane
Detected: 2.8 UG/L (ppb)
10/1/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 9 MG/L (ppm)
7/9/2025
Sulfate
Detected: 58 MG/L (ppm)
7/9/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 23 MG/L (ppm)
7/9/2025
Calcium
Detected: 18.6 MG/L (ppm)
7/9/2025
Potassium
Detected: 2 MG/L (ppm)
7/9/2025
Sodium
Detected: 16 MG/L (ppm)
7/9/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Hardness, Total (ASCACO3)
Detected: 142 MG/L (ppm)
7/9/2025
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
Bromide
Detected: 0.018 MG/L (ppm)
4/17/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 105 MG/L (ppm)
7/9/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dichloroaceticacid
Detected: 5.8 UG/L (ppb)
7/9/2025
Trichloroaceticacid
Detected: 23 UG/L (ppb)
7/9/2025
Dibromoaceticacid
Detected: 1.6 UG/L (ppb)
1/8/2025
Monochloroaceticacid
Detected: 2 UG/L (ppb)
4/2/2025
Alkalinity, Total
Detected: 105 MG/L (ppm)
7/9/2025
Carbon, Total
Detected: 2.5 MG/L (ppm)
7/9/2025
Silica
Detected: 14 MG/L (ppm)
7/9/2025
Chlorinedioxide
Detected: 1.5 MG/L (ppm)
7/9/2025
TDS
Detected: 188 MG/L (ppm)
7/9/2025
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.