What is the lowest point on the inside of a pipeline called?

The term "invert" refers specifically to the lowest interior point of a pipeline, where the liquid collects and begins its flow. It serves as the reference point for hydraulic calculations and is crucial for ensuring proper drainage and flow behavior within the system. Understanding the invert level is essential for engineers when designing drainage systems, as it affects factors like flow velocity and capacity.

The other terms may appear relevant, but they do not accurately represent the lowest point within a pipe. For instance, "flow line" typically denotes the theoretical line where liquid would flow within the pipe under certain conditions, rather than the physical lowest point. "Pipe bottom" and "base level" may refer to general positions within the context of pipelines but lack the specific definition that "invert" carries in the study of hydraulics and wastewater management.