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Water Quality Lookup / California / Stanislaus County
EPA SDWIS ยท Stanislaus County, California ยท 442 providers profiled

Stanislaus County, CA Water Quality Report

Stanislaus County is served by 442 major public water systems on file with the EPA.

Data current as of July 2026
๐Ÿ”Straight from EPA
๐ŸงชReal Lab Results
๐Ÿ“…Updated Quarterly
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Results for Stanislaus County, CA

442 water providers on file for this county, sorted by population served.

Quick answer: Stanislaus County has 442 water providers profiled, sorted by population served.

Violations on file

Nitrate
Older/archived health-based violation
Found at 50 of 442 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Coliform (TCR)
Older/archived health-based violation
Found at 25 of 442 providers
Arsenic
Older/archived health-based violation
Found at 16 of 442 providers
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Fluoride
Older/archived health-based violation
Found at 4 of 442 providers
Often added deliberately for dental health; can also occur naturally.
Selenium
Older/archived health-based violation
Found at 4 of 442 providers
Lead And Copper Rule Revisions
Currently open health violation
Found at 16 of 442 providers
Mercury
Older/archived health-based violation
Found at 1 of 442 providers
Combined Uranium
Older/archived health-based violation
Found at 4 of 442 providers
A naturally occurring radioactive metal. Long-term exposure above the legal limit is associated with kidney effects and increased cancer risk.
Revised Total Coliform Rule
Currently open health violation
Found at 3 of 442 providers

Contaminants found

Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.012 mg/L (ppm)
Found at 140 providers
Chromium, Hex
Detected: 21 UG/L (ppb)
Found at 71 providers
Iron
Detected: 2390 UG/L (ppb)
Found at 18 providers
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Barium
Detected: 232 UG/L (ppb)
Found at 15 providers
Arsenic
Detected: 21 UG/L (ppb)
Found at 39 providers
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Manganese
Detected: 4700 UG/L (ppb)
Found at 16 providers
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Lead
Detected: 174 UG/L (ppb)
Found at 9 providers
A metal that can leach from old pipes, solder, and fixtures. Current medical guidance holds there is no truly safe level of lead exposure, especially for children and pregnant women.
Copper, Free
Detected: 243 UG/L (ppb)
Found at 19 providers
Iron, Dissolved
Detected: 300 UG/L (ppb)
Found at 2 providers
Chromium
Detected: 33 UG/L (ppb)
Found at 6 providers
Occurs in two forms โ€” trivalent (an essential nutrient in trace amounts) and hexavalent (linked to increased cancer risk).
Combined Uranium
Detected: 75 PCI/L
Found at 12 providers
A naturally occurring radioactive metal. Long-term exposure above the legal limit is associated with kidney effects and increased cancer risk.
Vanadium, Total
Detected: 34 UG/L (ppb)
Found at 8 providers
Selenium
Detected: 19 UG/L (ppb)
Found at 7 providers
Zinc
Detected: 730 UG/L (ppb)
Found at 9 providers
Aluminum
Detected: 1200 UG/L (ppb)
Found at 4 providers
Mercury
Detected: 18 UG/L (ppb)
8/5/2025
Cadmium
Detected: 1.4 UG/L (ppb)
2/3/2025
Copper Summary
Detected: 1.402269 mg/L (ppm)
Found at 2 providers
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 42.9 UG/L (ppb)
Found at 16 providers
TTHM
Detected: 69.32 UG/L (ppb)
Found at 23 providers
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: 57.8 UG/L (ppb)
Found at 14 providers
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromoform
Detected: 36.01 UG/L (ppb)
Found at 17 providers
Bromodichloromethane
Detected: 13 UG/L (ppb)
Found at 15 providers
Dibromochloromethane
Detected: 24 UG/L (ppb)
Found at 18 providers
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Nitrate
Detected: 26 MG/L (ppm)
Found at 133 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Chloride
Detected: 1300 MG/L (ppm)
Found at 27 providers
Sulfate
Detected: 2800 MG/L (ppm)
Found at 28 providers
Fluoride
Detected: 0.68 MG/L (ppm)
Found at 21 providers
Often added deliberately for dental health; can also occur naturally.
Nitrate-Nitrite
Detected: 20.1 MG/L (ppm)
Found at 21 providers
Boron, Total
Detected: 5200 UG/L (ppb)
Found at 7 providers
Nitrite
Detected: 0.51 MG/L (ppm)
Found at 2 providers
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 440 MG/L (ppm)
Found at 34 providers
Potassium
Detected: 8.8 MG/L (ppm)
Found at 21 providers
Calcium
Detected: 270 MG/L (ppm)
Found at 37 providers
Sodium
Detected: 1300 MG/L (ppm)
Found at 31 providers
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Gross Alpha Particle Activity
Detected: 60.9 PCI/L
Found at 14 providers
Hardness, Total (ASCACO3)
Detected: 2360 MG/L (ppm)
Found at 32 providers
pH
Detected: 8.5 PH
Found at 23 providers
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
Langelier Index (pH(s))
Detected: 1 LANG
Found at 10 providers
pH, Field
Detected: 8.29 PH
Found at 8 providers
Orthophosphate
Detected: 1.1 MG/L (ppm)
10/22/2025
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
Lithium
Detected: 84.5 ยตg/L (ppb)
Found at 6 providers
Occurs naturally in some groundwater. Not currently federally regulated in drinking water.
PFOS
Detected: 0.024 ยตg/L (ppb)
Found at 2 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
PFHXS
Detected: 0.0069 ยตg/L (ppb)
Found at 2 providers
PFOA
Detected: 0.012 ยตg/L (ppb)
Found at 2 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
PFHXA
Detected: 0.0074 ยตg/L (ppb)
Found at 2 providers
PFPEA
Detected: 0.0084 ยตg/L (ppb)
Found at 2 providers
PFHPA
Detected: 0.0047 ยตg/L (ppb)
Found at 2 providers
PFBS
Detected: 0.0066 ยตg/L (ppb)
Found at 2 providers
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
1, 2, 3-Trichloropropane
Detected: 0.1347 UG/L (ppb)
Found at 14 providers
Tetrachloroethylene
Detected: 1.8 UG/L (ppb)
9/2/2025
Bromide
Detected: 0.13 MG/L (ppm)
10/2/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 602 MG/L (ppm)
Found at 36 providers
Alkalinity, Carbonate
Detected: 10.6 MG/L (ppm)
1/23/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dibromoaceticacid
Detected: 4 UG/L (ppb)
Found at 12 providers
Aggressive Index
Detected: 13.05 AGGR
Found at 21 providers
Alkalinity, Total
Detected: 602 MG/L (ppm)
Found at 37 providers
TDS
Detected: 6800 MG/L (ppm)
Found at 29 providers
Perfluorobutanesulfonicacid (PFBS)
Detected: 6.9 NG/L (ppt)
Found at 6 providers
Perfluoropfmba
Detected: 4.6 NG/L (ppt)
6/11/2025
Perfluorohexanoicacid (PFHXA)
Detected: 9.1 NG/L (ppt)
Found at 6 providers
Perfluoropentanoicacid (PFPEA)
Detected: 7.9 NG/L (ppt)
Found at 6 providers
Perfluoropfeesa
Detected: 5.1 NG/L (ppt)
6/11/2025
Hfpo-Da
Detected: 5.1 NG/L (ppt)
6/11/2025
Perfluorohexanesulfonicacid4:2fts
Detected: 5.1 NG/L (ppt)
6/11/2025
Perfluoropfmpa
Detected: 4.4 NG/L (ppt)
6/11/2025
Perfluoropentanesulfonicacid (PFPES)
Detected: 5.2 NG/L (ppt)
Found at 2 providers
Perfluoroheptanoicacid (PFHPA)
Detected: 4.5 NG/L (ppt)
Found at 5 providers
Adona
Detected: 4.1 NG/L (ppt)
6/11/2025
Perfluorooctanesulfonicacid6:2fts
Detected: 4.8 NG/L (ppt)
6/11/2025
Perfluoroheptanesulfonicacid (PFHPS)
Detected: 5.6 NG/L (ppt)
6/11/2025
Nonafluoronfdha
Detected: 4.7 NG/L (ppt)
6/11/2025
Perfluorohexanesulfonicacid (PFHxS)
Detected: 8.4 NG/L (ppt)
Found at 4 providers
9cl-Pf3ons
Detected: 4.7 NG/L (ppt)
6/11/2025
Perfluoroctanesulfonicacid (PFOS)
Detected: 7 NG/L (ppt)
Found at 5 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perfluoroctanoicacid (PFOA)
Detected: 6.7 NG/L (ppt)
Found at 6 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perfluorononanoicacid (PFNA)
Detected: 4.5 NG/L (ppt)
Found at 2 providers
Perfluorodecanesulfonicacid8:2fts
Detected: 4.7 NG/L (ppt)
6/11/2025
Conductivity (at 25ยฐC)
Detected: 8300 UMHO/CM
Found at 30 providers
Dichloroaceticacid
Detected: 9.8 UG/L (ppb)
Found at 11 providers
Trichloroaceticacid
Detected: 36.7 UG/L (ppb)
Found at 11 providers
1, 2-Dibromo-3-Chloropropane
Detected: 0.34 UG/L (ppb)
Found at 5 providers
Turbidity
Detected: 51 NTU
Found at 20 providers
A measure of water cloudiness from suspended particles.
Perchlorate
Detected: 4.3 UG/L (ppb)
Found at 6 providers
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
Adsorbableorganicfluorine
Detected: 3300 NG/L (ppt)
6/17/2025
Perfluorobutanoicacid (PFBA)
Detected: 5 NG/L (ppt)
Found at 5 providers
Color
Detected: 140 UNITS
Found at 7 providers
Monochloroaceticacid
Detected: 3 UG/L (ppb)
Found at 2 providers
Temperature (CENTIGRADE)
Detected: 23.4 C
Found at 2 providers
Odor
Detected: 2 TON
Found at 4 providers
Carbon, Total
Detected: 2 MG/L (ppm)
Found at 4 providers
Nitrogen-Ammoniaas (N)
Detected: 0.14 MG/L (ppm)
Found at 2 providers
Gross Beta Particle Activity
Detected: 5.22 PCI/L
8/7/2025
Bromate
Detected: 1.9 UG/L (ppb)
2/6/2025
Monobromoaceticacid
Detected: 1 UG/L (ppb)
1/2/2025
Silica
Detected: 74 MG/L (ppm)
Found at 2 providers
Radium-228
Detected: 0.258 PCI/L
8/15/2025
Radium-226
Detected: 0.53 PCI/L
10/1/2025
Filtration considerations: General system types, not a specific product recommendation.
Contaminant Whole-House Carbon Under-Sink RO Under-Sink Carbon
Total Trihalomethanes (TTHM)YesYesYes
Haloacetic Acids (HAA5)YesYesYes
ChloroformYesYesYes
Chlorine / TasteYesYesYes
Sediment / TurbidityYesYesYes
TrichloroethyleneYesYesYes
TetrachloroethyleneYesYesYes
cis-1,2-DichloroethyleneYesYesYes
1,1-DichloroethyleneYesYesYes
BromoformYesYesYes
BromodichloromethaneYesYesYes
DibromochloromethaneYesYesYes
1,1,2-TrichloroethaneYesYesYes
Vinyl ChlorideYesYesYes
Carbon TetrachlorideYesYesYes
BenzeneYesYesYes
TolueneYesYesYes
XyleneYesYesYes
Totalhaloaceticacids (HAA5)YesYesYes
1, 2, 3-TrichloropropaneYesYesYes
BromideYesYesYes
LeadPartialYesPartial
ArsenicPartialYesPartial
Chromium-6 (Hexavalent)PartialYesPartial
CopperPartialYesPartial
Combined UraniumPartialYesPartial
PFOAPartialYes*Partial
PFOSPartialYes*Partial
NitratePartialYesPartial
Combined RadiumPartialYesPartial
DibromoaceticacidPartialYesPartial
Chromium, HexPartialYesPartial
LithiumPartialYes*Partial
Aggressive IndexPartialYesPartial
Alkalinity, TotalPartialYesPartial
TDSPartialYesPartial
ChloridePartialYesPartial
SulfatePartialYesPartial
Perfluorobutanesulfonicacid (PFBS)PartialYesPartial
PerfluoropfmbaPartialYesPartial
Perfluorohexanoicacid (PFHXA)PartialYesPartial
Perfluoropentanoicacid (PFPEA)PartialYesPartial
PerfluoropfeesaPartialYesPartial
Hfpo-DaPartialYesPartial
Perfluorohexanesulfonicacid4:2ftsPartialYesPartial
PerfluoropfmpaPartialYesPartial
Perfluoropentanesulfonicacid (PFPES)PartialYesPartial
Perfluoroheptanoicacid (PFHPA)PartialYesPartial
AdonaPartialYesPartial
Perfluorooctanesulfonicacid6:2ftsPartialYesPartial
Perfluoroheptanesulfonicacid (PFHPS)PartialYesPartial
NonafluoronfdhaPartialYesPartial
Perfluorohexanesulfonicacid (PFHxS)PartialYesPartial
9cl-Pf3onsPartialYesPartial
Perfluoroctanesulfonicacid (PFOS)PartialYesPartial
Perfluoroctanoicacid (PFOA)PartialYesPartial
Perfluorononanoicacid (PFNA)PartialYesPartial
Perfluorodecanesulfonicacid8:2ftsPartialYesPartial
IronPartialYesPartial
BariumPartialYesPartial
Conductivity (at 25ยฐC)PartialYesPartial
DichloroaceticacidPartialYesPartial
TrichloroaceticacidPartialYesPartial
1, 2-Dibromo-3-ChloropropanePartialYesPartial
ManganesePartialYesPartial
Copper, FreePartialYesPartial
Iron, DissolvedPartialYesPartial
PerchloratePartialYesPartial
FluoridePartialYesPartial
Nitrate-NitritePartialYesPartial
Boron, TotalPartialYesPartial
ChromiumPartialYesPartial
PFHXSPartialYes*Partial
PFHXAPartialYes*Partial
PFPEAPartialYes*Partial
PFHPAPartialYes*Partial
PFBSPartialYes*Partial
AdsorbableorganicfluorinePartialYesPartial
Perfluorobutanoicacid (PFBA)PartialYesPartial
Combined UraniumPartialYesPartial
NitritePartialYesPartial
ColorPartialYesPartial
MonochloroaceticacidPartialYesPartial
Vanadium, TotalPartialYesPartial
SeleniumPartialYesPartial
ZincPartialYesPartial
Temperature (CENTIGRADE)PartialYesPartial
OdorPartialYesPartial
Carbon, TotalPartialYesPartial
Nitrogen-Ammoniaas (N)PartialYesPartial
Gross Beta Particle ActivityPartialYesPartial
BromatePartialYesPartial
MonobromoaceticacidPartialYesPartial
SilicaPartialYesPartial
AluminumPartialYesPartial
MercuryPartialYesPartial
CadmiumPartialYesPartial
Radium-226PartialYesPartial
Coliform Bacteria (indicator)NoYesNo
Gross Alpha Particle ActivityNoNoNo
MagnesiumNoPartialNo
PotassiumNoPartialNo
CalciumNoPartialNo
Alkalinity, BicarbonateNoNoNo
Hardness, Total (ASCACO3)NoNoNo
pHNoNoNo
Langelier Index (pH(s))NoNoNo
SodiumNoPartialNo
pH, FieldNoNoNo
Alkalinity, CarbonateNoNoNo
OrthophosphateNoNoNo

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What is TTHM? Understanding EPA Violation Status Is Chromium-6 Dangerous? Whole-House vs. Under-Sink Filtration Lead and Copper in Drinking Water What is PFAS? Arsenic and Uranium Explained Nitrate and Fluoride Explained Water Hardness, pH, and Turbidity What is Coliform Bacteria?