What is a mainline?
- Distribution mainlines around the city of Los Angeles deliver water to individual services and convey water between distribution supply facilities. These pipes take water from the trunk lines and run down neighborhood streets.
- Over 30% of LADWP’s mainlines are more than 80 years old.
- Based on LADWP’s analysis, 6% of LADWP’s mainlines are classified as a high priority. Factors are:
- Leak History
- Age of Pipe
- Soil Conditions
- Risk of Service interruption and community disruptions
- Coordination with planned projects by StreetsLA
- Additional Water System improvement projects
2024-25 Achievement(s)
- Installed approx. 240,800 ft of mainline pipe
- Installed approx. 11,500 ft of earthquake resilient pipe
2025-26 Goal: Replace 240,000 ft of mainline pipe
Long-Term Goal(s)
- Continue to replace 240,000 ft of mainline pipe each fiscal year to maintain a 150-year replacement cycle
- Reduce distribution life cycle costs, including capital, operations, and maintenance costs
- Continue installation of earthquake-resilient pipe and build our seismic-resilient pipe networks
- Replace high priority and most critical mainlines
What is a trunk line?
- Trunk lines are the arterial pipes moving large volumes of water from reservoirs to neighborhoods.
- 547 miles of trunk line pipe through Los Angeles
- Larger than 20 inches in diameter
2024-25 Achievement: Installed 5,266 feet of trunk line pipe
2025-26 Goal: Replace 6,047 feet of trunk line pipe
Long-Term Goal(s)
- By FY 2029-2030, LADWP will accelerate replacement to 3.5 miles/year of high-risk trunk lines.
- Enhance trunk line resilience through the use of earthquake-resilient pipe
Trunk lines are like freeways and mainlines are like neighborhood streets.
Leaks
The LADWP system experiences 2-4 water pipe breaks per day.
LADWP proactively monitors the water system for leaks using a variety of technologies and practices.
Achieved a 36% lower average leak rate (16.1 leaks per 100 miles) than the national industry average of 25 leaks per 100 miles in FY 24-25 (Water Research Foundation, 2017)
LADWP’s water loss rate is 6%, also lower than the national average.
The water system is highly pressurized moving large amounts of water across the city. When responding to water main breaks and crews need to turn off the water before repairing a ruptured pipe, the valves need to be closed carefully and slowly to avoid further damage elsewhere in the system.
