W hat is the best technique for inspecting water mains? The answer depends on what type of pipes a system has and whether a utility prefers to react to problems as they occur or prevent them from happening at all.The authors studied old and new leak detection techniques for metallic and prestressed concrete water pipes. The techniques that were compared and contrasted included water audits, sonic and acoustic leak detection, remote field inspection, magnetic flux leakage, ultrasound, corrosion measurement, visual inspection and tapping, and impact echo-spectral analysis of surface waves. Water audits, leak detection, and remote field inspection turned out to be the best approaches for inspecting cast-iron mains. Prestressed concrete cylinder pipe is best evaluated with acoustic emissions monitoring and remote field inspection. Additionally, because many of these techniques complement rather than compete with one another, a thorough diagnostic program is likely to use a combination of methods. These techniques can also be useful beyond just detecting leaks. For instance, a water audit can help evaluate the effectiveness of repairs. The remote-field-effect method can detect damage and pitting in pipes before they leak, and soil corrosivity analysis can show areas in pipes that are more susceptible to corrosion and subsequent failure. Thus, water suppliers can take a more active role in managing their systems and make better decisions regarding when it is necessary to protect pipes and whether it makes more sense to repair or replace them.-LPS

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