The Uni-Bell PVC Pipe Association has set up a Watermain Break Clock site showing real time numbers and costs of water main breaks. According to the information posted, there are 850 water main breaks that occur each day in North America. A quick search on Twitter gives us a snapshot of just a few of these: http://twitter.com/#!/search/water%20main%20break. (I've also added a widget on the side showing a stream of tweets talking about water main breaks.)
In the last city where I worked, ductile iron or cast iron pipes were used for main construction up until about 1990. It was about that year that we started putting in PVC for new mains or for replacements. In the 20 years I worked in that area, all of our breaks were on the metal pipe, and we probably averaged 10 to 20 breaks a year.
Of course, the PVC mains were new – by the time I left that job, the oldest PVC main we had was about 20 years old. So did the PVC perform better because of the material or age? Where I work now, they have been using ductile iron exclusively for main construction so obviously all of our breaks are on metal pipes – I think we have about 20 to 40 a year.
But over the last few months I have been working on a water main extension project to install about 1300 feet of new main. We priced out the pipe the other day and compared the PVC costs with the ductile iron costs – PVC was cheaper by half. With the economy the way it is, I believe we will be buying the PVC pipe, and based on the data on this site, it looks like we'll be preventing some future main breaks.