Water is often disinfected before it enters the distribution system to ensure that potentially dangerous microbes handful of households may be relatively simple. Large metropolitan water systems can be extremely complex. sometimes with thousands of miles of piping serving millions of people. Although water may be safe when leaving the water treatment plant it is important to ensure that this water does not become contaminated in the distribution system because of such things as water main breaks, pressure problems, or growth of microorganisms. Much of the existing drinking water infrastructure was built many years ago. The US EPA Infrastructure Needs Survey, released in 2001,