Detecting Leaks in Water-Distribution Pipes

In most water-distribution systems, a large percentage of the water is lost in transit from treatment plants to consumers. The amount of water that is lost or unaccounted for is typically 20-30 percent of production.1 Some systems, especially older ones, may lose as much as 50 percent. Water loss can be attributed to several causes, including leakage, metering errors, public usage such as fire-fighting and pipe flushing, and theft. Leakage is usually the major cause. Leakage occurs in different components of the distribution system: transmission pipes, distribution pipes, service connection pipes, joints, valves, and fire hydrants. Causes of leaks include corrosion, material defects, faulty installation, excessive water pressure, water hammer, ground movement due to drought or freezing, and excessive loads and vibration from road traffic. Leaks waste both money and a precious natural resource, and they create a public health risk. The primary economic loss is the cost of raw water, its treatment, and its transportation. Leakage leads to additional economic loss in the form of damage to the pipe network itself, e.g., erosion of pipe bedding and pipe breaks, and to the foundations of roads and buildings (Figure 1). Risk to public health can be caused by contaminants entering the pipe through leak openings if water pressure in the distribution system is lost. Economic constraints, concern over public health risk and the need to conserve water all motivate water system operators to implement leakage-control programs. Systematic leakage-control programs have two main components: water audits and leak-detection surveys. In recent years, significant efforts have been made to develop water audit procedures and leak-detection methods. As a result, water system operators now have several wellestablished procedures2 and modern equipment to help them control water loss. Detecting Leaks in Water-Distribution Pipes