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Water Quality Lookup / California / San Joaquin County
EPA SDWIS Β· San Joaquin County, California Β· 571 providers profiled

San Joaquin County, CA Water Quality Report

San Joaquin County is served by 571 major public water systems on file with the EPA.

Data current as of July 2026
πŸ”Straight from EPA
πŸ§ͺReal Lab Results
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Results for San Joaquin County, CA

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

Quick answer: San Joaquin County has 571 water providers profiled, sorted by population served.

Violations on file

Coliform (TCR)
Older/archived health-based violation
Found at 37 of 571 providers
Arsenic
Older/archived health-based violation
Found at 14 of 571 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.
Nitrate
Older/archived health-based violation
Found at 25 of 571 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Nitrate-Nitrite
Older/archived health-based violation
Found at 3 of 571 providers
Lead And Copper Rule Revisions
Currently open health violation
Found at 20 of 571 providers
Selenium
Older/archived health-based violation
Found at 1 of 571 providers
Fluoride
Older/archived health-based violation
Found at 1 of 571 providers
Often added deliberately for dental health; can also occur naturally.
Revised Total Coliform Rule
Older/archived health-based violation
Found at 2 of 571 providers
Tetrachloroethylene
Older/archived health-based violation
Found at 1 of 571 providers

Contaminants found

Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.069 mg/L (ppm)
Found at 205 providers
Lead
Detected: 36 UG/L (ppb)
Found at 16 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: 740 UG/L (ppb)
Found at 45 providers
Arsenic
Detected: 23 UG/L (ppb)
Found at 78 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.
Chromium, Hex
Detected: 26.4 UG/L (ppb)
Found at 134 providers
Barium
Detected: 859 UG/L (ppb)
Found at 32 providers
Combined Uranium
Detected: 17 PCI/L
Found at 21 providers
A naturally occurring radioactive metal. Long-term exposure above the legal limit is associated with kidney effects and increased cancer risk.
Iron
Detected: 5640 UG/L (ppb)
Found at 28 providers
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Manganese
Detected: 1740 UG/L (ppb)
Found at 36 providers
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Vanadium, Total
Detected: 34 UG/L (ppb)
Found at 26 providers
Nickel
Detected: 17 UG/L (ppb)
Found at 3 providers
Chromium
Detected: 31 UG/L (ppb)
Found at 23 providers
Occurs in two forms β€” trivalent (an essential nutrient in trace amounts) and hexavalent (linked to increased cancer risk).
Zinc
Detected: 2890 UG/L (ppb)
Found at 18 providers
Copper Summary
Detected: 3.931 mg/L (ppm)
Found at 3 providers
Selenium
Detected: 55 UG/L (ppb)
Found at 7 providers
Iron, Dissolved
Detected: 50 UG/L (ppb)
9/3/2025
Aluminum
Detected: 610 UG/L (ppb)
Found at 6 providers
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
TTHM
Detected: 66 UG/L (ppb)
Found at 22 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.
Bromoform
Detected: 17 UG/L (ppb)
Found at 20 providers
Bromodichloromethane
Detected: 10.6 UG/L (ppb)
Found at 18 providers
Dibromochloromethane
Detected: 17.86 UG/L (ppb)
Found at 20 providers
Chloroform
Detected: 60 UG/L (ppb)
Found at 16 providers
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Totalhaloaceticacids (HAA5)
Detected: 27 UG/L (ppb)
Found at 15 providers
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Nitrate
Detected: 17 MG/L (ppm)
Found at 223 providers
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Sulfate
Detected: 306 MG/L (ppm)
Found at 33 providers
Chloride
Detected: 360 MG/L (ppm)
Found at 40 providers
Fluoride
Detected: 0.2 MG/L (ppm)
Found at 39 providers
Often added deliberately for dental health; can also occur naturally.
Nitrate-Nitrite
Detected: 11.4 MG/L (ppm)
Found at 22 providers
Boron, Total
Detected: 1800 UG/L (ppb)
Found at 16 providers
Nitrite
Detected: 0.4 MG/L (ppm)
6/9/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 42 MG/L (ppm)
Found at 36 providers
Potassium
Detected: 10 MG/L (ppm)
Found at 35 providers
Sodium
Detected: 152 MG/L (ppm)
Found at 37 providers
Calcium
Detected: 113 MG/L (ppm)
Found at 37 providers
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
pH
Detected: 8.13 PH
Found at 9 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: 1.4 LANG
Found at 32 providers
Hardness, Total (ASCACO3)
Detected: 442 MG/L (ppm)
Found at 36 providers
Orthophosphate
Detected: 0.48 MG/L (ppm)
Found at 2 providers
Gross Alpha Particle Activity
Detected: 25.5 PCI/L
Found at 37 providers
pH, Field
Detected: 8.13 PH
Found at 29 providers
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
PFOS
Detected: 0.0135 Β΅g/L (ppb)
Found at 6 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
PFPEA
Detected: 0.0033 Β΅g/L (ppb)
Found at 2 providers
PFHPA
Detected: 0.0033 Β΅g/L (ppb)
2/15/2024
PFHXS
Detected: 0.018 Β΅g/L (ppb)
Found at 5 providers
PFOA
Detected: 0.0079 Β΅g/L (ppb)
Found at 4 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
PFHXA
Detected: 0.0095 Β΅g/L (ppb)
Found at 3 providers
PFBS
Detected: 0.0075 Β΅g/L (ppb)
Found at 4 providers
Lithium
Detected: 47 Β΅g/L (ppb)
Found at 3 providers
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: 0.04 UG/L (ppb)
Found at 8 providers
Trichloroethylene
Detected: 9 UG/L (ppb)
Found at 2 providers
Tetrachloroethylene
Detected: 47 UG/L (ppb)
Found at 4 providers
Cis-1, 2-Dichloroethylene
Detected: 1.7 UG/L (ppb)
Found at 2 providers
1, 1-Dichloroethylene
Detected: 1.7 UG/L (ppb)
10/1/2025
Dichlorodifluoromethane
Detected: 16.8 UG/L (ppb)
9/3/2025
Bromide
Detected: 0.16 MG/L (ppm)
9/30/2025
Ethylenedibromide
Detected: 0.33 UG/L (ppb)
2/19/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 510 MG/L (ppm)
Found at 37 providers
Other
Additional substances tested that don't fit neatly into the categories above
Dibromoaceticacid
Detected: 7 UG/L (ppb)
Found at 18 providers
Conductivity (at 25Β°C)
Detected: 2000 UMHO/CM
Found at 40 providers
Aggressive Index
Detected: 12.4 AGGR
Found at 34 providers
Silica
Detected: 79.6 MG/L (ppm)
Found at 2 providers
Alkalinity, Total
Detected: 420 MG/L (ppm)
Found at 36 providers
TDS
Detected: 1230 MG/L (ppm)
Found at 41 providers
Turbidity
Detected: 45 NTU
Found at 28 providers
A measure of water cloudiness from suspended particles.
Radium-228
Detected: 1.92 PCI/L
Found at 9 providers
Color
Detected: 40 UNITS
Found at 12 providers
1, 2-Dibromo-3-Chloropropane
Detected: 0.38 UG/L (ppb)
Found at 16 providers
Odor
Detected: 32 TON
Found at 10 providers
Foamingagents (SURFACTANTS)
Detected: 0.087 MG/L (ppm)
5/6/2025
Perfluorohexanesulfonicacid (PFHxS)
Detected: 8.7 NG/L (ppt)
Found at 13 providers
Perfluoroctanesulfonicacid (PFOS)
Detected: 18 NG/L (ppt)
Found at 15 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perfluoroctanoicacid (PFOA)
Detected: 27 NG/L (ppt)
Found at 15 providers
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Dichloroaceticacid
Detected: 12 UG/L (ppb)
Found at 14 providers
Trichloroaceticacid
Detected: 11 UG/L (ppb)
Found at 12 providers
Monochloroaceticacid
Detected: 12 UG/L (ppb)
Found at 9 providers
Langelier Index (Source Temp.)
Detected: 0.82 LANG
Found at 2 providers
Carbon, Total
Detected: 2.5 MG/L (ppm)
Found at 4 providers
Perfluorobutanoicacid (PFBA)
Detected: 15 NG/L (ppt)
Found at 9 providers
Monobromoaceticacid
Detected: 1.3 UG/L (ppb)
4/10/2025
Perfluorohexanoicacid (PFHXA)
Detected: 15 NG/L (ppt)
Found at 11 providers
Radium-226
Detected: 0.27 PCI/L
8/13/2025
Combined Radium (-226 & -228)
Detected: 0.62 PCI/L
8/20/2025
A naturally occurring radioactive element found in some groundwater.
Perfluorobutanesulfonicacid (PFBS)
Detected: 10 NG/L (ppt)
Found at 6 providers
Perfluoroheptanoicacid (PFHPA)
Detected: 4.9 NG/L (ppt)
Found at 6 providers
Perfluorononanoicacid (PFNA)
Detected: 2.5 NG/L (ppt)
8/4/2025
Perfluoropentanoicacid (PFPEA)
Detected: 13 NG/L (ppt)
Found at 10 providers
Perfluoropentanesulfonicacid (PFPES)
Detected: 2.8 NG/L (ppt)
Found at 2 providers
Perfluoroheptanesulfonicacid (PFHPS)
Detected: 2.2 NG/L (ppt)
2/10/2025
Adsorbableorganicfluorine
Detected: 860 NG/L (ppt)
Found at 3 providers
Temperature (CENTIGRADE)
Detected: 17.3 C
10/27/2025
Perchlorate
Detected: 1.1 UG/L (ppb)
7/2/2025
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
TotalradiumforntncperΒ§64442(B) (3)
Detected: 0.47 PCI/L
Found at 2 providers
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
1, 2, 3-TrichloropropaneYesYesYes
Totalhaloaceticacids (HAA5)YesYesYes
DichlorodifluoromethaneYesYesYes
BromideYesYesYes
EthylenedibromideYesYesYes
LeadPartialYesPartial
ArsenicPartialYesPartial
Chromium-6 (Hexavalent)PartialYesPartial
CopperPartialYesPartial
Combined UraniumPartialYesPartial
PFOAPartialYes*Partial
PFOSPartialYes*Partial
NitratePartialYesPartial
Combined RadiumPartialYesPartial
DibromoaceticacidPartialYesPartial
Copper, FreePartialYesPartial
SulfatePartialYesPartial
ChloridePartialYesPartial
Chromium, HexPartialYesPartial
BariumPartialYesPartial
Conductivity (at 25Β°C)PartialYesPartial
Aggressive IndexPartialYesPartial
SilicaPartialYesPartial
Alkalinity, TotalPartialYesPartial
TDSPartialYesPartial
FluoridePartialYesPartial
Nitrate-NitritePartialYesPartial
Combined UraniumPartialYesPartial
Boron, TotalPartialYesPartial
IronPartialYesPartial
ManganesePartialYesPartial
Vanadium, TotalPartialYesPartial
NickelPartialYesPartial
ChromiumPartialYesPartial
ZincPartialYesPartial
ColorPartialYesPartial
1, 2-Dibromo-3-ChloropropanePartialYesPartial
SeleniumPartialYesPartial
Iron, DissolvedPartialYesPartial
OdorPartialYesPartial
Foamingagents (SURFACTANTS)PartialYesPartial
NitritePartialYesPartial
Perfluorohexanesulfonicacid (PFHxS)PartialYesPartial
Perfluoroctanesulfonicacid (PFOS)PartialYesPartial
Perfluoroctanoicacid (PFOA)PartialYesPartial
DichloroaceticacidPartialYesPartial
TrichloroaceticacidPartialYesPartial
MonochloroaceticacidPartialYesPartial
PFPEAPartialYes*Partial
PFHPAPartialYes*Partial
PFHXSPartialYes*Partial
PFHXAPartialYes*Partial
PFBSPartialYes*Partial
Langelier Index (Source Temp.)PartialYesPartial
Carbon, TotalPartialYesPartial
AluminumPartialYesPartial
LithiumPartialYes*Partial
Perfluorobutanoicacid (PFBA)PartialYesPartial
MonobromoaceticacidPartialYesPartial
Perfluorohexanoicacid (PFHXA)PartialYesPartial
Radium-226PartialYesPartial
Combined Radium (-226 & -228)PartialYesPartial
Perfluorobutanesulfonicacid (PFBS)PartialYesPartial
Perfluoroheptanoicacid (PFHPA)PartialYesPartial
Perfluorononanoicacid (PFNA)PartialYesPartial
Perfluoropentanoicacid (PFPEA)PartialYesPartial
Perfluoropentanesulfonicacid (PFPES)PartialYesPartial
Perfluoroheptanesulfonicacid (PFHPS)PartialYesPartial
AdsorbableorganicfluorinePartialYesPartial
Temperature (CENTIGRADE)PartialYesPartial
PerchloratePartialYesPartial
TotalradiumforntncperΒ§64442(B) (3)PartialYesPartial
Coliform Bacteria (indicator)NoYesNo
pHNoNoNo
Langelier Index (pH(s))NoNoNo
MagnesiumNoPartialNo
PotassiumNoPartialNo
SodiumNoPartialNo
CalciumNoPartialNo
Hardness, Total (ASCACO3)NoNoNo
Alkalinity, BicarbonateNoNoNo
OrthophosphateNoNoNo
Gross Alpha Particle ActivityNoNoNo
pH, FieldNoNoNo

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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?