Water rationing caused pipe breaks in LA

During the summer of 2009 a large number of water pipe breaks occurred in Los Angeles. Apparently,ֲ  there were 101 blowouts in the summer of 2009 (July, August and September) compared to 42 in 2008, 49 in 2007 and 48 in 2006. As a consequence of the public request for an explanation an independent investigation was requested to study the cause of these blowouts. Last week the experts review was published and the findings are fascinating:

The Investigation Teamג€™s findings reveal a connection between the Cityג€™s water-rationing program and the increase in pipe breaks during the summer of 2009, especially with cast iron pipes. At various locations in the LADWP water distribution system, the water pressure dropped significantly on Mondays and Thursdays after the beginning of the water rationing program on June 1, 2009. Those water pressure drops on these days were caused by an increased water flow during the watering of lawns. As a result, the cyclic levels of water pressure increased and accelerated the metal fatigue failures of aged and corroded cast iron pipes.
These findings conclude that that the sudden changes of water pressure in the system, attributable to the water-rationing program, had a negative impact on cast iron pipes with lower fatigue resistance (i.e. especially corroded cast iron pipes).

The cyclic pressure drops on Mondays and Thursdays is shown from the recorded data:

In the conclusions the experts team write:

There is evidence that the cyclic amplitudes of internal water pressure increased due to water rationing and contributed to the failure of cast iron pipes by metal fatigue. At various locations in the LADWP water distribution system, the water pressure dropped significantly on Mondays and Thursdays after June 1, 2009, when the water-rationing program began in Los Angeles. Temporary drops in water pressure on these days were caused by increased water flow during the watering of lawns. The expert review team study has shown that increased amplitudes of cyclic daily pressure can have a negative impact on pipe materials with lower fatigue resistance, especially corroded cast iron pipes. Fatigue effects on cast iron pipes do not appear immediately, but accumulate gradually. Cycling at increased amplitudes of pressure accumulated gradually in June through September, 2009 as aging cast iron pipes with low fatigue resistance were subjected
to elevated pressure cycles. Fatigue-related pipeline breaks resulted in pipe failures (referred to as blowouts), which raised concerns from the media and the public because of the damage they caused to street pavements and properties.

Additional resources (opens in new windows):

• The full report.
• An updated map showing pipe breaks in the LA water network is available on Google maps.
• TV coverage by KABC