Distribution Systems

Aging Water Infrastructure

From the late 1800s through the late 1960s, most distribution pipes installed in the U.S. were manufactured from cast iron. The failure rate of these older pipes has increased over time and the pipes may be reaching the end of their respective service lives at about the same time. This will increase the financial burden on public water utilities because the cost of replacement will be borne over a shorter time span than that of the original installation period.

Small private drinking water systems tend to have more miles of pipe in place than public systems (when comparing the same system service population size). Most of the piping replacement each year is done in the private rather than the public sector and very large systems replace more piping per year than smaller systems.

About 23 percent of public small system pipelines are over 40 years old, and some are over 80. However, most small public water system pipes are less than 40 years old. Here's the breakout:

• Less than 40 years old: 77.6 to 80.5 percent
• Between 40 and 80 years old: 17.5 to 19.4 percent
• More than 80 years old: 0.1 to 4.0 percent

For small private water system pipes, the breakout is as follows:

• Less than 40 years old: 92.6 to 98.7 percent
• Between 40 and 80 years old: 1.3 to 7.4 percent
• More than 80 years old: 0.0 to 0.6 percent

For small public water systems, repair or installation of water mains provides a potential route for direct contamination of the distribution system. For example, the piping materials may be exposed to contaminants (such as animal wastes or polluted stormwater runoff) at the manufacturer before construction activities have begun. At the construction site, the interiors of pipes and fittings can come into contact with soil and water, both potential sources of bacterial contamination. After construction, contamination can occur from external sources (such as unsanitary water infiltrating into the distribution system through leaking pipe joints).

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