Serving roughly 26,240 people in Los Angeles County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for GSWC-SOUTH SAN GABRIEL
1 water provider directly on file, serving roughly 26,240 people in Los Angeles County, California.
Quick answer: GSWC-SOUTH SAN GABRIEL has no violations on file and no single reading stands out against its peers (601 other providers in this area). It serves roughly 26,240 people, and the full breakdown below reflects everything EPA and California have on record for it.
Lead Summary
PFBA
Lithium
TTHM
Bromoform
Dibromochloromethane
Chloroform
Bromodichloromethane
Dibromoaceticacid
Dichloroaceticacid
Trichloroaceticacid
Nitrate
Perfluorobutanoicacid (PFBA)
Perfluoroctanesulfonicacid (PFOS)
Perfluoroctanoicacid (PFOA)
Perfluorobutanesulfonicacid (PFBS)
Tetrachloroethylene
Perchlorate
Trichloroethylene
Aggressive Index
Magnesium
Sodium
Calcium
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Sulfate
Chloride
Fluoride
Perfluorohexanesulfonicacid (PFHxS)
Perfluoroheptanoicacid (PFHPA)
Perfluorononanoicacid (PFNA)
Perfluorodecanoicacid (PFDA)
Perfluorohexanoicacid (PFHXA)
Perfluoropentanoicacid (PFPEA)
Turbidity
Combined Uranium
pH
Chromium, Hex
Chromium
Utility GSWC-SOUTH SAN GABRIELPopulation served 26,240Owner Private
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)
12/31/2023
Combined Uranium
Detected: 3.3 PCI/L
5/30/2025
A naturally occurring radioactive metal. Long-term exposure above the legal limit is associated with kidney effects and increased cancer risk.
Chromium, Hex
Detected: 3.9 UG/L (ppb)
5/13/2025
Chromium
Detected: 3.8 UG/L (ppb)
5/13/2025
Occurs in two forms — trivalent (an essential nutrient in trace amounts) and hexavalent (linked to increased cancer risk).
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
TTHM
Detected: 37 UG/L (ppb)
10/22/2025
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: 4.6 UG/L (ppb)
10/22/2025
Dibromochloromethane
Detected: 14 UG/L (ppb)
10/22/2025
Chloroform
Detected: 7.8 UG/L (ppb)
10/22/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromodichloromethane
Detected: 11 UG/L (ppb)
10/22/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Nitrate
Detected: 2.8 MG/L (ppm)
10/22/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Sulfate
Detected: 54 MG/L (ppm)
6/30/2025
Chloride
Detected: 18 MG/L (ppm)
6/30/2025
Fluoride
Detected: 0.78 MG/L (ppm)
5/30/2025
Often added deliberately for dental health; can also occur naturally.
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 16 MG/L (ppm)
6/30/2025
Sodium
Detected: 26 MG/L (ppm)
6/30/2025
Calcium
Detected: 50 MG/L (ppm)
6/30/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Hardness, Total (ASCACO3)
Detected: 190 MG/L (ppm)
6/30/2025
pH
Detected: 7.9 PH
6/30/2025
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
PFBA
Detected: 0.0056 µg/L (ppb)
4/11/2024
Lithium
Detected: 40 µg/L (ppb)
7/9/2024
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
Tetrachloroethylene
Detected: 1.4 UG/L (ppb)
8/27/2025
Trichloroethylene
Detected: 0.87 UG/L (ppb)
7/15/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 160 MG/L (ppm)
6/30/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dibromoaceticacid
Detected: 1.1 UG/L (ppb)
10/22/2025
Dichloroaceticacid
Detected: 1.9 UG/L (ppb)
10/22/2025
Trichloroaceticacid
Detected: 1.8 UG/L (ppb)
10/22/2025
Perfluorobutanoicacid (PFBA)
Detected: 2.7 NG/L (ppt)
7/15/2025
Perfluoroctanesulfonicacid (PFOS)
Detected: 5.7 NG/L (ppt)
7/15/2025
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perfluoroctanoicacid (PFOA)
Detected: 3.8 NG/L (ppt)
7/15/2025
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perfluorobutanesulfonicacid (PFBS)
Detected: 2.5 NG/L (ppt)
7/15/2025
Perchlorate
Detected: 1.5 UG/L (ppb)
10/16/2025
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
Aggressive Index
Detected: 12 AGGR
6/30/2025
Alkalinity, Total
Detected: 160 MG/L (ppm)
6/30/2025
TDS
Detected: 310 MG/L (ppm)
6/30/2025
Perfluorohexanesulfonicacid (PFHxS)
Detected: 3 NG/L (ppt)
7/15/2025
Perfluoroheptanoicacid (PFHPA)
Detected: 2.1 NG/L (ppt)
5/30/2025
Perfluorononanoicacid (PFNA)
Detected: 2 NG/L (ppt)
5/30/2025
Perfluorodecanoicacid (PFDA)
Detected: 1.9 NG/L (ppt)
5/30/2025
Perfluorohexanoicacid (PFHXA)
Detected: 2.3 NG/L (ppt)
5/30/2025
Perfluoropentanoicacid (PFPEA)
Detected: 2 NG/L (ppt)
5/30/2025
Turbidity
Detected: 0.2 NTU
6/30/2025
A measure of water cloudiness from suspended particles.
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.