What is a tubercle in the context of water distribution systems?

In the context of water distribution systems, a tubercle refers to a rust crust that forms due to the corrosion of pipes, particularly in iron or steel piping systems. This corrosion process occurs when water interacts with the metal, leading to the formation of rust, which can aggregate over time into small, protruding formations known as tubercles. These tubercles can significantly impact water flow by reducing the internal diameter of pipes, leading to an increase in hydraulic resistance and potentially causing blockages. Understanding this phenomenon is crucial for the maintenance and management of water distribution systems as it directly affects the efficiency and quality of water delivery.