What does poly pigging do in a water main?

Poly pigging in a water main is primarily used to remove tuberculation and sediments that accumulate inside the pipe. This process involves the use of a "pig," a device that is propelled through the pipeline. The pig can be designed with scraping or brushing mechanisms that effectively clean the interior surface of the pipe as it moves through it, helping to restore capacity and water quality.

Removing tuberculation—mineral deposits that can develop along the inner walls of pipes—improves flow efficiency and mitigates issues related to water quality. This cleaners action addresses both buildup and sediment, making it a vital part of maintaining water distribution systems.

Other options focus on different aspects of pipeline maintenance. Cleaning the exterior of the pipe deals with a different maintenance issue, while testing for leaks relates to the integrity of the pipeline rather than cleaning. Similarly, autonomous inspection pertains to evaluating the condition of the pipe rather than actively cleaning it. Therefore, the primary function of poly pigging is aligned with option B, making it the correct response.