What is the term for the lowest point on the inside of a pipe?

The term for the lowest point on the inside of a pipe is "the invert." This is an important concept in civil engineering and wastewater management because the invert elevation of a pipe is critical for ensuring proper flow and drainage. It provides information about the flow characteristics inside the pipe, allowing engineers to design systems that prevent blockages and support gravitational flow. Knowing the invert level helps in assessing the capacity of the drainage system, maintaining proper slopes, and conducting maintenance. Understanding this term is essential for professionals working with sewer systems and ensuring operational integrity.

The other options represent different aspects of pipes or structures. For instance, "the crown" refers to the highest point of the pipe's internal surface, typically at the top of the pipe, which is relevant for understanding the shape of a sewer. "The rim" is commonly used to describe the upper edge of a manhole or a catch basin, while "the base" isn't a standard term used to refer to any specific point in a pipe's structure. Therefore, the defining characteristics of the invert make it the correct term for this measurement.