Wednesday, April 14, 2010

Hydraulic LCF in LA Water Systems

Heard an ironic, and somewhat ridiculous story (link here) on the radio just now, that water conservation regulations in Los Angeles - where lawn watering was prohibited on some days, and allowed on other days - lead to pressure spikes and troughs that lead to widespread failures (101 failures in a year, more than double the previous years' records) in cast iron pipes, most of which were 30 years old or more. Human behavior, it's so predictable!

LA residents, in fear of fines - and some wanting to be environmentally conscious - didn't water on the restricted days, and then the allowable days, BAM, everyone opens the spigots around town. Cast iron's LCF (low cycle fatigue) properties are pretty pathetic, from an over-all comparative material strength perspective. Couple this low resistance to cyclical stresses with an aging, corroding, under-capacity metropolitan water system built on massive fault lines, and it is no wonder the number of failures are climbing.


  1. Here in Reno, odd-numbered addresses water on 3 days of the week, and even addresses water on 3 different days per week. It evens out the load. The 7th day (Monday) is some kind of catch-up day for the water system. Watering is also not allowed during the hottest hours to reduce waste from evaporation. All seems reasonable to me.

  2. And on the 7th day, the Utility rested...


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