Across the country, a surge of service line leaks and failures is plaguing drinking water utilities. They’re spending tens of millions of dollars to replace lines that connect mains in the street to meters typically located curbside. In addition to per-line replacement costs ranging from $1,800 in Las Vegas to $4,000 in Northern California, the process leaves behind an unsightly patchwork of street repairs.
The scale of the problem is daunting.
In a region that fully realizes the cost of “lost water,” Nevada’s Las Vegas Valley Water District is replacing about 56,000 polyethylene (PE) lines at a pace of more than 2,200 per year. In Rio Rancho, N.M., almost one-half of the 3,914 leaks documented from January 2007 to December 2011 occurred in just 2010 and 2011. The city’s water service provider, CH2M Hill, estimates that replacing all 14,400 service lines would take two full-time crews about 14 years and cost $40.4 million.
The root of the problem: the unforeseen consequences of integrating older and newer pipeline materials.
Missing link leads to leaks
Historically, most service lines were copper tube. The material worked well, even in corrosive soils, because the pipe was often connected to cast-iron water mains that acted as large anodes and shielded the more noble copper from corrosion.
However, the use of asbestos cement and plastic water mains has inadvertently eliminated the “sacrificial anode.” As a result, it’s not unusual for copper service lines in corrosive soils to develop outside-in pinhole leaks in eight to 10 years.
Once viewed as more corrosion-resistant and less costly than copper, polybutylene (PB) and PE service lines are also failing because of contact with chlorine-based disinfectants. Other failure modes include installation problems (bedding and handling), cyclic fatigue, and undetected material flaws.
Thus, not only are water mains and transmission lines suffering from age and accelerating degradation, the smaller capillaries that feed homes and businesses face a similar need for rehabilitation.
