This program lets you define the tailwater condition at the outlet as either Free Outfall, Crown Elevation or User-Specified.

For a pipe with a hydraulically steep slope, the Free Outfall condition will yield a starting depth equal to normal depth in the pipe. For a pipe with a hydraulically mild slope, the Free Outfall condition will yield a starting depth equal to critical depth. When an outlet has multiple incoming pipes, the Free Outfall condition yields a starting elevation equal to the lowest of the individual computed elevations.

The Crown condition should be used when the pipe discharges to an outlet where the water surface elevation is equal to the elevation of the top of the pipe.