Drinking Water Quality Monitoring Results
Tables I, II and III list the results of water tests performed by the LADWP and MWD from January to December 2025. LADWP tests for over 200 substances. These tables include only substances with values that are detected. No substance was detected above the maximum contaminant level.
Table I
Health-based Primary Drinking Water Standards (MCLs)
State PHG Substances Detected in Treated Water
Table I (CONT’D)
Health-based Primary Drinking Water Standards (MCLs)
Substances Detected in Treated Water and Reported on City-Wide Basis
Tables I, II and III list the results of water tests performed by the LADWP and MWD from January to December 2025. LADWP tests for over 200 substances. These tables include only substances with values that are detected. No substance was detected above the maximum contaminant level.
Abbreviations and Terms used in Tables:
AL Regulatory Action Level: The concentration of a contaminant which, if exceeded, triggers treatment or other requirements that a water system must follow.
Compliance: Meeting a drinking water standard based on the health risk (primary standards) and aesthetic (secondary standards) exposure of a contaminant to consumers. For example, bacteria and nitrate have strict limits that must be met at all times due to the acute effects they can cause. Other standards, like small amounts of disinfection by-products and man-made chemicals, have standards that are based on a lifetime of exposure because the risk to consumers is very low. Compliance with most standards is based on an average of samples collected within a year. This allows for some fluctuation above and below the numerical standard, while still protecting public health.
MRL Federal Minimum Reporting Level: The minimum concentration of a contaminant which can be detected in drinking water using analytical methods established by the U.S. EPA. Data reported in Table IV reflect MRLs.
MCL Maximum Contaminant Level: The highest level of a contaminant that is allowed in drinking water. Primary MCLs are set as close to the PHGs (or MCLGs) as is economically and technologically feasible. Secondary MCLs are set to protect the odor, taste, and appearance of drinking water.
MCLG Maximum Contaminant Level Goal: The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs are set by the USEPA.
MRDL Maximum Residual Disinfectant Level: The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
MRDLG Maximum Residual Disinfectant Level Goal: The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
NL Notification Level: A health-based advisory level established by SWRCB-DDW for chemicals in drinking water that lack MCLs.
PDWS Primary Drinking Water Standard: MCLs, MRDLs and treatment techniques (TTs) for contaminants that affect health, along with their monitoring and reporting requirements.
PHG Public Health Goal: The level of a contaminant in drinking water below which there is no known or expected risk to health. PHGs are set by the California Environmental Protection Agency.
SMCL Secondary Maximum Contaminate Level: The highest level a constituent allowed in drinking water that may affect the taste, odor or appearance. SMCLs are set by the U.S. EPA.
DLR State Detection Limit: A detected contaminant at or above its detection level for reporting purposes. DLRs are set by the SWRCB-DDW. Data reported in Tables I, II, and III reflect DLRs.
TT Treatment Technique: A required process intended to reduce the level of a contaminant in drinking water. For example, the filtration process is a treatment technique used to reduce turbidity (cloudiness in water) and microbial contaminants from surface water. High turbidities may be indicative of poor or inadequate filtration.
HOW TO READ THE TABLES
For San Fernando Valley Area – water test results are under the Los Angeles Aqueduct Filtration Plant, the Northern Combined Wells, and the MWD Jensen Plant columns.
For Central Los Angeles Area – water test results are under the Los Angeles Aqueduct Filtration Plant and the Southern Combined Wells columns.
For Western Los Angeles Area – water test results are under the Los Angeles Aqueduct Filtration Plant columns.
For Harbor/Eastern Los Angeles Area – water test results are under MWD Weymouth, MWD Diemer, and MWD Jensen Plants columns.
Some substances are reported on a City-wide basis as required by the State Water Board.
Table Abbreviations and Footnotes
(please refer to the Abbreviations and Terms Section for other abbreviations and definitions)
ACU = apparent color unit
CFU/mL = colony-forming unit per milliliter < = less than the detection limit for reporting purposes
μg/L = micrograms per liter (equivalent to ppb)
μS/cm = microsiemens per centimeter
mg/L = milligrams per liter (equivalent to ppm)
NTU = nephelometric turbidity units
NA = not applicable
NR = not reported
NT = not tested
NUM/100 mL = number per 100 milliliters % = percentage
pCi/L = picocuries per liter
TON = threshold odor number
C =Celsius