COASTSIDE COUNTY WATER DISTRICT Water Quality Report
Serving roughly 18,940 people in San Mateo County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
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Results for COASTSIDE COUNTY WATER DISTRICT
1 water provider directly on file, serving roughly 18,940 people in San Mateo County, California.
Quick answer: COASTSIDE COUNTY WATER DISTRICT has no violations on file and no single reading stands out against its peers (113 other providers in this area). It serves roughly 18,940 people, and the full breakdown below reflects everything EPA and California have on record for it.
Lead Summary
Aggressive Index
Langelier Index (pH(s))
Langelier Index (Source Temp.)
Magnesium
Sodium
Calcium
Hardness, Total (ASCACO3)
Bromide
Alkalinity, Total
Alkalinity, Bicarbonate
TDS
Chloride
Sulfate
Fluoride
Nitrate-Nitrite
Nitrate
Turbidity
pH
Chromium, Hex
Barium
Selenium
Conductivity (at 25°C)
Color
Potassium
Carbon, Total
Odor
Iron
Manganese
Aluminum
Utility COASTSIDE COUNTY WATER DISTRICTPopulation served 18,940Owner Local government
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.0016 mg/L (ppm)
12/31/2024
Chromium, Hex
Detected: 0.098 UG/L (ppb)
1/8/2025
Barium
Detected: 37 UG/L (ppb)
4/2/2025
Selenium
Detected: 2.1 UG/L (ppb)
4/2/2025
Iron
Detected: 672 UG/L (ppb)
10/1/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Manganese
Detected: 60 UG/L (ppb)
10/1/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Aluminum
Detected: 45 UG/L (ppb)
10/1/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 64 MG/L (ppm)
4/2/2025
Sulfate
Detected: 37 MG/L (ppm)
4/2/2025
Fluoride
Detected: 0.2 MG/L (ppm)
4/2/2025
Often added deliberately for dental health; can also occur naturally.
Nitrate-Nitrite
Detected: 3.5 MG/L (ppm)
4/2/2025
Nitrate
Detected: 3.2 MG/L (ppm)
8/6/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 6.4 MG/L (ppm)
10/1/2025
Sodium
Detected: 16 MG/L (ppm)
10/1/2025
Calcium
Detected: 21 MG/L (ppm)
10/1/2025
Potassium
Detected: 0.7 MG/L (ppm)
10/1/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Langelier Index (pH(s))
Detected: 0.26 LANG
10/1/2025
Hardness, Total (ASCACO3)
Detected: 78 MG/L (ppm)
10/1/2025
pH
Detected: 7.6 PH
9/24/2025
A measure of how acidic or basic the water is (7 is neutral). Affects taste and plumbing, not a direct health measure.
VOCs (Volatile Organic Compounds)
Industrial solvents and fuel-related chemicals that evaporate easily
Bromide
Detected: 0.2 MG/L (ppm)
4/2/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 159 MG/L (ppm)
4/2/2025
Other
Additional substances tested that don't fit neatly into the categories above
Aggressive Index
Detected: 11.5 AGGR
10/1/2025
Langelier Index (Source Temp.)
Detected: -0.57 LANG
10/1/2025
Alkalinity, Total
Detected: 85 MG/L (ppm)
9/24/2025
TDS
Detected: 338 MG/L (ppm)
4/2/2025
Turbidity
Detected: 1.7 NTU
9/24/2025
A measure of water cloudiness from suspended particles.
Conductivity (at 25°C)
Detected: 558 UMHO/CM
4/2/2025
Color
Detected: 3 UNITS
4/2/2025
Carbon, Total
Detected: 2.41 MG/L (ppm)
9/24/2025
Odor
Detected: 2 TON
4/2/2025
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.