Serving roughly 69,973 people in Santa Clara County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
🏠Local Expertise
Results for CWSC LOS ALTOS SUBURBAN
1 water provider directly on file, serving roughly 69,973 people in Santa Clara County, California.
Quick answer: CWSC LOS ALTOS SUBURBAN has no violations on file. One reading is worth knowing about: Alkalinity, Total was measured at 280MG/L, among the highest of the 320 providers on file in this area. It's the most notable figure in this system's record among its 320 local peers.
Lead Summary
PFHXS
Aggressive Index
Langelier Index (pH(s))
Magnesium
Potassium
Sodium
Calcium
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Chloride
Sulfate
Fluoride
Nitrate
Nitrate-Nitrite
Perfluorohexanesulfonicacid (PFHxS)
Perfluorohexanoicacid (PFHXA)
Perfluoroctanesulfonicacid (PFOS)
pH, Field
Boron, Total
Strontium
Iron
Dichlorodifluoromethane
Lead
Vanadium, Total
Manganese
Chromium, Hex
Perchlorate
Nickel
Chromium
Barium
Cyanide
Copper, Free
Zinc
Conductivity (at 25°C)
Temperature (CENTIGRADE)
Utility CWSC LOS ALTOS SUBURBANPopulation served 69,973Owner Private
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.0015 mg/L (ppm)
12/31/2025
Strontium
Detected: 360 UG/L (ppb)
6/9/2025
Iron
Detected: 23 UG/L (ppb)
9/17/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Lead
Detected: 11 UG/L (ppb)
3/12/2025
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.
Vanadium, Total
Detected: 8.8 UG/L (ppb)
6/11/2025
Manganese
Detected: 1.6 UG/L (ppb)
9/17/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Chromium, Hex
Detected: 2.1 UG/L (ppb)
10/22/2025
Nickel
Detected: 1.1 UG/L (ppb)
9/17/2025
Chromium
Detected: 5.3 UG/L (ppb)
9/17/2025
Occurs in two forms — trivalent (an essential nutrient in trace amounts) and hexavalent (linked to increased cancer risk).
Barium
Detected: 62 UG/L (ppb)
9/17/2025
Copper, Free
Detected: 1.5 UG/L (ppb)
9/17/2025
Zinc
Detected: 2.3 UG/L (ppb)
9/17/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 42 MG/L (ppm)
8/12/2025
Sulfate
Detected: 46 MG/L (ppm)
8/12/2025
Fluoride
Detected: 0.2 MG/L (ppm)
9/17/2025
Often added deliberately for dental health; can also occur naturally.
Nitrate
Detected: 7 MG/L (ppm)
9/17/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Nitrate-Nitrite
Detected: 2.6 MG/L (ppm)
6/9/2025
Boron, Total
Detected: 112 UG/L (ppb)
9/17/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 27 MG/L (ppm)
9/8/2025
Potassium
Detected: 1.2 MG/L (ppm)
9/17/2025
Sodium
Detected: 43 MG/L (ppm)
9/17/2025
Calcium
Detected: 82 MG/L (ppm)
9/17/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Langelier Index (pH(s))
Detected: -0.009 LANG
8/12/2025
Hardness, Total (ASCACO3)
Detected: 331 MG/L (ppm)
8/12/2025
pH, Field
Detected: 7.65 PH
10/23/2025
PFAS & Emerging Contaminants
Human-made "forever chemicals" and other substances not yet fully regulated
PFHXS
Detected: 0.0031 µg/L (ppb)
4/10/2024
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
Dichlorodifluoromethane
Detected: 2.6 UG/L (ppb)
3/12/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 280 MG/L (ppm)
8/12/2025
Other
Additional substances tested that don't fit neatly into the categories above
Aggressive Index
Detected: 12.1 AGGR
8/12/2025
Alkalinity, Total
Detected: 280 MG/L (ppm)
8/12/2025
TDS
Detected: 440 MG/L (ppm)
8/12/2025
Perfluorohexanesulfonicacid (PFHxS)
Detected: 3.6 NG/L (ppt)
10/15/2025
Perfluorohexanoicacid (PFHXA)
Detected: 2.9 NG/L (ppt)
10/15/2025
Perfluoroctanesulfonicacid (PFOS)
Detected: 3.1 NG/L (ppt)
7/9/2025
One of two PFAS with an enforceable federal limit (4 ppt) since 2024.
Perchlorate
Detected: 2.3 UG/L (ppb)
10/23/2025
Can occur naturally or from industrial/military sources; may interfere with thyroid function at elevated levels.
Cyanide
Detected: 6 UG/L (ppb)
3/12/2025
Conductivity (at 25°C)
Detected: 730 UMHO/CM
6/9/2025
Temperature (CENTIGRADE)
Detected: 17.5 C
8/12/2025
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.