Deteriorating Buried Infrastructure
The rate of deterioration of a buried water system has little to do with the actual age of the material used but rather with external forces which have contributed to an increased amount of leaks, main breaks, taste, odor and color problems, reduction of water flow, internal pipe corrosion, need for more disinfectants, growth of biofilms, and regrowth of bacteria. Three different older types of cast- iron pipes installed mostly before the 1960s are about at the end of their service life. The problem is not only related to potential health risks and poor customer service, but also the enormous cost involved in replacing the buried water system. The estimated cost of replacement varies with the professional organization or governmental organization making the estimate, and the range of cost from 2002 to 2020 (in 2002 dollars) is $151-$220 billion for the United States. One of the great difficulties is determining when to replace a given section of pipe and the main.
There are numerous reasons why pipes fail. They are manufacturing defects; improper design or installation; geological instability; higher operating pressures; hydraulic transients (a sudden change in velocity of the water); change in water temperature (especially freezing temperatures); excessive external loads; damage from digging; internal corrosion; external corrosion from soil and other sources; leadite (a pipe-joining material) corrosion; incompatibility of materials; deterioration of gaskets; and material fatigue.