What reduces the carrying capacity of water mains?

The correct choice, tuberculation, refers to the formation of tubercles or protrusions on the interior surface of water pipes, typically composed of corrosion products, sediment, and biological growth. These tubercles create obstructions within the water main, leading to a reduced cross-sectional area for water flow. This reduction in flow area directly impacts the carrying capacity of the pipe, as the water encounters increased resistance and turbulence.

Tuberculation can also lead to more severe issues, such as increased pressure loss and diminished water quality, making it a significant concern in water distribution systems. Addressing tuberculation often requires cleaning and maintenance of the piping system to restore flow capacity and ensure efficient operation. In contrast, while pitting, corrosion, and scaling also affect water distribution infrastructure, they do so in different ways that may not directly result in the same characteristic obstruction that tuberculation causes.