Water Main Breaks

BACKGROUND

Crews pump water away from a broken main and dig to uncover the pipe.
Crews pump water away from a broken main and dig to uncover the pipe.

SFPUC operates and maintains 1,200 miles of water pipelines in San Francisco. Stretched end to end, these pipes, also called water mains, could stretch from San Francisco all the way to Dodge City, Kansas.  Approximately 20% of San Francisco’s water pipes are about 100 years old, and made of cast iron. Many water mains are aging and nearing the end of their working life. 

Although we have an active program to replace aging and vulnerable water mains each year, we are not able to prevent all water main breaks.  On average, there are between 100 to 200 water main breaks in our system per year.

Water mains in San Francisco vary greatly in size – from 5 feet in diameter to 2 inches in diameter. The flow of water in these pipes is stopped, started, and slowed by valves -- a lot like the faucets at home. 

SFPUC’s City Distribution Division personnel work 24/7 to monitor the system and respond to water main breaks, regardless of weather, holiday, or time of day.

Crews connect a new section of pipe to the main.

What Happens in a Typical Water Main Break

  • A leak or rushing water from a potential main break is reported to our City Distribution Division, usually through 311.
  • A senior valve operator – called a Gateman – drives to the scene to investigate and confirm a water main break.
  • The Gateman contacts the Underground Service Alert system (USA) who will then send a field technician to mark all utilities, such as gas lines,  prior to any digging. This may take some time, particularly if the break occurs at night.  
  • A foreman dispatches a Main Break Response Team to the site. The core Response Team includes: one foreman, two plumbers, a laborer, one truck driver and one backhoe operator. Additional staff such as machinists, carpenters to reinforce trenches, and welders might be needed depending upon the particulars of the water main break.
Crews bring the main back into service before filling the hole and prep for temporary paving.
  • The team usually establishes traffic control, such as flaggers and cones, high warning signs and arrow boards to safely direct traffic around the work area.
  • An operator uses a backhoe to open up the street and dig out a hole above the broken water main. All materials are placed on a truck to be hauled away.
  • The excavated pit is often filled with water. Crews use pumps to remove the water to allow personnel to inspect the main and diagnose the issue. 
  • Once crews identify a remedy, the Gateman will close the necessary valves to shut off water to the area around the broken pipe so that repairs may proceed.
  • When this happens, water service to customers connected to the water main would be temporarily impacted. This might be low water pressure or no water pressure.  Crews are careful to minimize the number of customers affected by a water main break.
  • Crews either place a special clamp on the broken portion of the pipe or remove and install an entirely new piece of pipe to repair the break. The repair method varies depending upon the type of break and type of pipe.
  • Crews disinfect and flush the new line and bring it back into service.
  • When normal water service is restored, crews refill the hole, clean up, and put a temporary pavement patch on the work area.
  • Final restoration in the form of permanent paving often occurs at a later date. 

 

Frequently Asked Questions