Serving roughly 3,797 people in Mendocino County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for WILLOW COUNTY WATER DISTRICT
1 water provider directly on file, serving roughly 3,797 people in Mendocino County, California.
Quick answer: WILLOW COUNTY WATER DISTRICT has no violations on file. One reading is worth knowing about: Sulfate was measured at 20MG/L, among the highest of the 265 providers on file in this area. It's the most notable figure in this system's record among its 265 local peers.
Lead Summary
Copper Summary
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Bromodichloromethane
Dibromochloromethane
Dichloroaceticacid
Trichloroaceticacid
Dibromoaceticacid
Copper, Free
Aggressive Index
Magnesium
Sodium
Calcium
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Chloride
Sulfate
Nitrate
Radium-228
Combined Radium (-226 & -228)
pH
Boron, Total
Conductivity (at 25°C)
Color
Utility WILLOW COUNTY WATER DISTRICTPopulation served 3,797Owner Local government
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0 mg/L (ppm)
12/31/2025
Copper Summary
Detected: 1.5 mg/L (ppm)
12/31/2023
Copper, Free
Detected: 160 UG/L (ppb)
9/18/2025
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 8.9 UG/L (ppb)
9/8/2025
TTHM
Detected: 10.1 UG/L (ppb)
9/8/2025
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: 5.75 UG/L (ppb)
9/8/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromodichloromethane
Detected: 2.82 UG/L (ppb)
9/8/2025
Dibromochloromethane
Detected: 1.53 UG/L (ppb)
9/8/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 8.4 MG/L (ppm)
9/11/2025
Sulfate
Detected: 20 MG/L (ppm)
9/11/2025
Nitrate
Detected: 1 MG/L (ppm)
9/11/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Boron, Total
Detected: 210 UG/L (ppb)
9/11/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 15 MG/L (ppm)
9/11/2025
Sodium
Detected: 11 MG/L (ppm)
9/11/2025
Calcium
Detected: 26 MG/L (ppm)
9/11/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Hardness, Total (ASCACO3)
Detected: 127 MG/L (ppm)
9/11/2025
pH
Detected: 6.87 PH
9/11/2025
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 110 MG/L (ppm)
9/11/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dichloroaceticacid
Detected: 5.5 UG/L (ppb)
9/8/2025
Trichloroaceticacid
Detected: 2.3 UG/L (ppb)
9/8/2025
Dibromoaceticacid
Detected: 1.1 UG/L (ppb)
9/8/2025
Aggressive Index
Detected: 10.72 AGGR
9/11/2025
Alkalinity, Total
Detected: 110 MG/L (ppm)
9/11/2025
TDS
Detected: 180 MG/L (ppm)
9/11/2025
Radium-228
Detected: 0.737 PCI/L
9/8/2025
Combined Radium (-226 & -228)
Detected: 0.737 PCI/L
9/8/2025
A naturally occurring radioactive element found in some groundwater.
Conductivity (at 25°C)
Detected: 280 UMHO/CM
9/11/2025
Color
Detected: 5 UNITS
9/8/2025
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.