Serving roughly 43,357 people in Contra Costa County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
🏠Local Expertise
Results for DIABLO WATER DISTRICT
1 water provider directly on file, serving roughly 43,357 people in Contra Costa County, California.
Quick answer: DIABLO WATER DISTRICT has no violations on file. One reading is worth knowing about: Nitrogen-Ammoniaas (N) was measured at 0.55MG/L, among the highest of the 179 providers on file in this area. It's the most notable figure in this system's record among its 179 local peers.
Lead Summary
Lithium
Magnesium
Calcium
Sodium
Alkalinity, Total
Alkalinity, Bicarbonate
Hardness, Total (ASCACO3)
TDS
Chloride
Sulfate
Fluoride
Nitrate-Nitrite
Nitrate
Turbidity
Radium-228
Combined Radium (-226 & -228)
Gross Alpha Particle Activity
Gross Beta Particle Activity
pH
Odor
Manganese
Arsenic
Conductivity (at 25°C)
Color
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Bromoform
Bromodichloromethane
Dibromochloromethane
Dichloroaceticacid
Trichloroaceticacid
Dibromoaceticacid
Potassium
Nitrogen-Ammoniaas (N)
Boron, Total
Chromium, Hex
Copper, Free
Utility DIABLO WATER DISTRICTPopulation served 43,357Owner Local government
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0.0019 mg/L (ppm)
12/31/2022
Manganese
Detected: 44.4 UG/L (ppb)
10/21/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Arsenic
Detected: 3.1 UG/L (ppb)
5/21/2025
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: 0.56 UG/L (ppb)
7/17/2025
Copper, Free
Detected: 17 UG/L (ppb)
7/17/2025
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 3.51 UG/L (ppb)
9/18/2025
TTHM
Detected: 17 UG/L (ppb)
9/18/2025
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.
Chloroform
Detected: 1.7 UG/L (ppb)
9/18/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromoform
Detected: 4.5 UG/L (ppb)
9/18/2025
Bromodichloromethane
Detected: 4.3 UG/L (ppb)
9/18/2025
Dibromochloromethane
Detected: 6.3 UG/L (ppb)
9/18/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Chloride
Detected: 57 MG/L (ppm)
7/17/2025
Sulfate
Detected: 70 MG/L (ppm)
7/17/2025
Fluoride
Detected: 0.71 MG/L (ppm)
7/17/2025
Often added deliberately for dental health; can also occur naturally.
Nitrate-Nitrite
Detected: 0.51 MG/L (ppm)
10/7/2025
Nitrate
Detected: 0.51 MG/L (ppm)
10/7/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Boron, Total
Detected: 300 UG/L (ppb)
8/5/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 15 MG/L (ppm)
7/17/2025
Calcium
Detected: 27 MG/L (ppm)
7/17/2025
Sodium
Detected: 54 MG/L (ppm)
7/17/2025
Potassium
Detected: 1 MG/L (ppm)
7/17/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Hardness, Total (ASCACO3)
Detected: 128 MG/L (ppm)
7/17/2025
Gross Alpha Particle Activity
Detected: 3.74 PCI/L
6/18/2025
pH
Detected: 8.04 PH
7/17/2025
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
Lithium
Detected: 13 µg/L (ppb)
9/11/2023
Occurs naturally in some groundwater. Not currently federally regulated in drinking water.
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 89.3 MG/L (ppm)
7/17/2025
Other
Additional substances tested that don't fit neatly into the categories above
Alkalinity, Total
Detected: 89.3 MG/L (ppm)
7/17/2025
TDS
Detected: 342 MG/L (ppm)
7/17/2025
Turbidity
Detected: 0.27 NTU
7/17/2025
A measure of water cloudiness from suspended particles.
Radium-228
Detected: 0.68 PCI/L
6/18/2025
Combined Radium (-226 & -228)
Detected: 0.715 PCI/L
6/18/2025
A naturally occurring radioactive element found in some groundwater.
Gross Beta Particle Activity
Detected: 16.8 PCI/L
6/18/2025
Odor
Detected: 3 TON
7/17/2025
Conductivity (at 25°C)
Detected: 455 UMHO/CM
7/17/2025
Color
Detected: 2 UNITS
5/21/2025
Dichloroaceticacid
Detected: 1.07 UG/L (ppb)
9/18/2025
Trichloroaceticacid
Detected: 2.63 UG/L (ppb)
3/6/2025
Dibromoaceticacid
Detected: 2.44 UG/L (ppb)
9/18/2025
Nitrogen-Ammoniaas (N)
Detected: 0.55 MG/L (ppm)
7/17/2025
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.