A fiberglass 10-inch Palmer-Bowlus Flume installed in a concrete manhole to measure sanitary flow.  

The Palmer-Bowlus Flume is designed to adapt well to measuring average to high sanitary flows in sewage systems. The flume is typically sized to match the line size - e.g. 10-inch flume for a 10-inch line - although it is possible to go up / down one flume size versus the line size - e.g. 10-inch flume on a 12-inch line.  You would not, however, want to select a Palmer-Bowlus Flume that is more than one size different than the line size.