Pipe X length is shorter than the elevation change

A Caution message in AFT Arrow

This caution alerts you to a possible inconsistency in your input. When this warning occurs, you have defined a pipe with a length that is shorter than the elevation change between its connecting junctions. This inconsistency may be an input error or a result of a component which itself has an elevation change. AFT Arrow only accepts a single elevation per junction, so if the error is due to the latter possibility, pipe lengths or junction elevations should be adjusted accordingly.