Flow Through the Device is Reversed
When the user draws a pipe, the assumed direction of flow for the network analysis is the direction in which the pipe is drawn, with the inlet at the node created when the pipe is first started and the outlet at the node created when the pipe is completed.
This warning will occur when PIPE-FLO completes the network analysis using the Conservation of Mass and Conservation of Energy and the calculated flow rate is in the opposite direction from which the connected pipes were drawn.
For closed looped systems, this may be an acceptable condition because one operating scenario may have fluid flowing in one direction, but flow in the opposite direction if boundary conditions change.
This may also be caused by the user drawing the pipe in the wrong direction.