Arizona Plumbing Practice Exam

What is the name for the inside bottom elevation of a sewer line or drain pipe?

1. Flow line

2. Drain grade

3. Invert

4. Pipe base

The correct answer is: Invert

The inside bottom elevation of a sewer line or drain pipe is referred to as the invert. This term specifically denotes the lowest point of a pipe's interior, where the flow of wastewater is at its base. Understanding the invert elevation is crucial in plumbing because it helps determine the proper slope of the sewer line or drain pipe, ensuring that gravity effectively aids in the movement of waste away from the plumbing system and reduces the risk of backups. In practical applications, knowing the invert is essential for proper system design, including the layout of drainage systems and the connection points of different pipe segments. The invert clearance also affects how sewage is managed within a municipal system or residential plumbing, affecting overall efficiency and function. The other terms, while related to aspects of drainage systems, do not specifically define the bottom elevation of the pipe. For instance, "flow line" refers generally to the path taken by the water or waste, "drain grade" can describe the slope of the drain but not necessarily its elevation, and "pipe base" is a less formal term that does not universally convey the precise measurements important for plumbing design.