Questions and Answers Regarding Main Breaks in
- What causes water main leaks?
Most leaks are the result of corrosion, a natural process that sees a thinning of the wall of the pipe due to a chemical breakdown based on environmental conditions (soil and water.) However, a pipe may break at a particular time because of the added stress of temperature change, surge in pressure or even construction impact.
- When a break occurs, why don’t crews shut off the water right away?
The water distribution system is an interconnected network of pipelines with large transmission lines and smaller local distribution lines with branches and loops to supply efficiently.
For a large flow of water, the system valves that are used to control both the flow and pressure must be shut down slowly and in the correct order so as not to damage the system and to impact as few customers as possible. A sudden shutting of a valve may cause a “water hammer” surge with the potential of breaking further sections of pipe.
Most leaks are repaired with the pipeline still in service at a reduced flow and pressure. By maintaining pressure in the pipeline, soil or water will not enter the line while it is out of service for repairs, thereby minimizing the need for further disinfection of the line and impact to customers.
- When do most leaks occur?
Leaks occur most frequently occur in December and January, when water entering the system from the Eastern Sierra is suddenly colder. The cold water causes pipes to shrink very slightly, known as thermal contraction.
Winter leaks occur most frequently in the early morning hours, between 3 a.m. and 5 a.m., when pressure is highest because of minimal use and the temperature is coldest.
- Why is the water from the Eastern Sierra so cold?
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- Can you predict when a pipe will break?
For the most part, the water pipeline system is buried. Some of the system was installed over 100 years ago under very different construction conditions than we have today. Pipe is installed throughout the City in many types of conditions. Therefore, we cannot easily excavate the pipe up to look at a pipe, nor do we have good methods of estimating its condition. There is technology for material imaging suitable for some types of pipe material. Water companies use one technology successfully on large diameter concrete pipe and the oil and gas industry uses it in their lines. LADWP continues to investigate these new technologies.
- Are we doing enough and working fast enough?
Since fiscal year 2006-07, LADWP has increased water main replacement from a goal of 50,000 feet to the current year goal of 110,000 feet. The long-term goal is to replace 200,000 feet by fiscal year 2013-14.
- How much money are we spending on pipeline Infrastructure?
The Water System budget for water main replacement in the current fiscal year is $38.8 million.
- On average, how many leaks does LADWP experience annually?
LADWP averages approximately 1400 water main leaks and breaks per year. Approximately 200 of these can be characterized as breaks requiring more significant repairs. These are leaks and breaks that impact customers, cause street closures and/or require street repairs in excess of 100 square feet. These breaks occasionally generate media attention, but frequently go unnoticed.
We experience on average approximately four breaks a day, which is an extraordinarily small number given the size and complexity of our water system. Additionally, most breaks or leaks require small spot repairs, not full replacements.
- What is the life span of a water pipe?
Most of the pipes in our system have an expected lifespan of 110 years. Those are made out of cast iron, welded steel or ductile iron. A small percentage (1.3%) of the pipes in our system are made out of riveted steel and have an expected lifespan of 90 years.
- How many customers are affected by water main leaks, and how?
On the average, 20 customers’ services may be affected by a water main break. Frequently, however, customers are not aware of any impact of a water main break to their service. Most leaks are repaired with the line in service or slightly below normal pressure.
Larger or more difficult breaks may require service be shut off. Typically customers within an individual block are affected. The Fire Department is notified if service to fire hydrants is impacted. On very rare occasions, when it is determined that a line should be fully replaced as opposed to repaired, customers are provided service from a temporary “sideline” for several weeks while a new main is fully installed.
- How do I report a water leak?
To report a leak or for any water trouble issue, please call 1-800- DIAL DWP (1-800-342-5397). Please provide as detailed information as possible including the address or intersection closest to the leak, a description of where the water is originating (fire hydrant, meter box, crack in pavement), a general description of the amount of water (trickle, moderate, flooding) and whether there is any apparent hazard or property damage.
- What steps are involved in repairing a water main?
As a crew approaches a leak, their first step is to assess the safety of the situation. The crew looks for downed power lines, erosion under the pavement and the general flow of traffic. The crew will evaluate what the likely source of water is, where the closest valves are, and which customers may be affected. Depending on the size of the facility, the crew will contact the Operation Control Group to coordinate major water routing.
Once traffic is controlled in the area, the crew is ready to start shutting down the flow of water. The line will either be completely closed down, or its flow and pressure will be reduced. The Los Angeles Fire Department, major customers, and officials are notified as appropriate. The Underground Service Alert is contacted if additional excavation is required.
As water and/or mud are removed, the crew assesses the type and size of pipe, extent of break and determines equipment and materials necessary to repair the main. As the equipment and materials are assembled, the crew continues to pump water and clear the site. The main line is repaired with a clamp (for minor leaks) or a section is removed and replaced for large breaks. The excavation is backfilled and paved with temporary paving. At a later date, after the area has dried and a contract can be scheduled, the temporary paving is removed and permanent paving completed. For larger areas, the City Bureau of Street Services completes the paving.
- How much water is lost when a water main breaks?
The amount of water leaking from a broken water pipe varies with the size of main, pressure and type of leak. For example, the amount of water lost during the main breaks that occurred in September 2009 is minimal. For the first three months of mandatory water conservation (June, July and August,) Angelenos conserved 30,000 acre feet of water. This equates to 10 billion gallons. The total water lost in the September main breaks is less than ½ of one percent of the water saved this summer.
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