Which method is NOT commonly used for leak detection in water pipelines?

Thermal imaging is typically not a common method used for leak detection in water pipelines compared to the other options listed. While thermal imaging can be useful in specific scenarios, it's more commonly applied in electrical or mechanical inspections to identify hot or cold spots, rather than in detecting water leaks specifically.

In contrast, pressure monitoring is a standard practice where fluctuations in pressure within a pipeline can indicate possible leaks. Visual inspections involve physically examining the pipeline for visible signs of leakage, such as wet spots or water pooling, making it a direct method of detection. Acoustic sensors detect the sounds made by water escaping under pressure from a leak, and they are often deployed in modern leak detection systems due to their effectiveness in pinpointing leaks that may not be visually accessible.

This context highlights that while thermal imaging has its applications, it does not play a central role in the routine detection of leaks in water pipelines.