Los Angeles Water Quality Guide: Imported Water and Treatment
Comprehensive guide to Los Angeles water quality, covering imported water sources, advanced treatment processes, and safety information.
Environmental Health Research
Health Information Reviewed
Health-related content reviewed by Michael Rodriguez, MSc, Public Health Consultant, to ensure public health recommendations are accurate and appropriate.
Last reviewed: April 2026
Water Source
Los Angeles obtains water from three primary sources: the Los Angeles Aqueduct system bringing water from the Eastern Sierra Nevada, the Metropolitan Water District (MWD) supplies from the Colorado River and State Water Project, and local groundwater. The Los Angeles Aqueduct, completed in 1913, historically provided the majority of the city's water from Owens Valley and Mono Basin. Today, imported water from MWD and groundwater make up increasing portions of the supply. The Los Angeles Department of Water and Power (LADWP) manages this complex portfolio serving nearly 4 million people.
Water Treatment Process
LADWP operates multiple treatment facilities tailored to different water sources. The LA Aqueduct Filtration Plant treats Eastern Sierra water using ozonation, coagulation, sedimentation, and filtration. MWD-supplied water is treated at regional facilities before delivery. Treatment includes advanced oxidation for taste and odor control, coagulation, sedimentation, filtration, and chloramine disinfection. UV treatment has been added at some facilities. LADWP also blends waters from different sources to optimize quality and taste throughout the distribution system.
Known Issues and Historical Concerns
Los Angeles has addressed various water quality challenges over the years while maintaining compliance with drinking water standards.
- Some areas have experienced elevated chromium-6 levels
- PFAS detected in some groundwater sources
- Disinfection byproducts from organic matter in source waters
- Lead concerns in older buildings with legacy plumbing
- Taste variations based on seasonal source water blending
- Perchlorate contamination affects some groundwater basins
- 1,2,3-TCP detected in portions of San Fernando Valley groundwater
- Aging infrastructure in some neighborhoods
Recent Improvements and Investments
LADWP continues major investments in water quality infrastructure and local supply development to improve quality and resilience.
- Expanded groundwater treatment for PFAS and chromium-6
- Invested over $1 billion in water system infrastructure
- Implemented advanced treatment at multiple facilities
- Developed stormwater capture and groundwater recharge projects
- Upgraded distribution system mains and service connections
- Enhanced real-time water quality monitoring
- Accelerated lead service line inventory and replacement
- Expanded recycled water programs for non-potable uses
EPA Compliance and Monitoring
Los Angeles water meets all federal and California state drinking water standards, which are among the strictest in the nation. LADWP conducts over 100,000 water quality tests annually, monitoring for more than 200 potential contaminants. California has established lower maximum contaminant levels than EPA for several substances, including chromium-6 and PFAS. Water quality reports are published annually and made available to all customers. LADWP participates in EPA monitoring programs for unregulated and emerging contaminants.
Note: For the most current water quality data, view the Los Angeles Water Quality Report which includes EPA SDWIS data and contaminant analysis.
Recommendations for Los Angeles Residents
LA tap water is safe to drink and rigorously tested, though filtration can provide additional benefits for some residents.
- 1Carbon filtration can improve taste and remove chloramine
- 2Check for lead in older buildings built before 1986
- 3Reverse osmosis recommended if concerned about chromium-6
- 4Run water for 30 seconds before drinking after long periods of non-use
- 5Review annual Water Quality Reports from LADWP
- 6Consider NSF 53 certified filters for lead reduction
- 7Report any unusual taste, odor, or color to LADWP
- 8Request free lead testing for qualifying older homes
Water Filter Options for Los Angeles
Based on Los Angeles's water quality profile, consider these filtration options:
Activated Carbon Filters
Good for improving taste, removing chlorine/chloramine, and filtering common organic compounds.
Reverse Osmosis Systems
Comprehensive filtration removing 95-99% of contaminants including lead, PFAS, and dissolved solids.
Related Resources
- Los Angeles, California Water Quality Report
View current contaminant data and quality scores
- California State Water Quality Overview
Compare water quality across California cities
- Home Water Testing Guide
How to test your water at home
- Complete Guide to Lead in Drinking Water
Understanding lead risks and mitigation
- How to Choose the Right Water Filter
Filter recommendations by contaminant type
- Water Filter Cost Calculator
Calculate the cost of different filtration options