In Los Angeles, they have basically given up on doing any preventive maintenance of the water/sewer lines. They just wait for something to break and replace it. We have areas with pipes over a 100 years old. Too expensive to dig up huge areas of the city to replace the lines all at once. This may also have something to do with the notoriously corrupt LA Dept. Of Water and power too. Other cities in LA County do periodically replace the lines, but it's still tremendously expensive.