The Gradually Varied Flow (GVF) rational solver does not directly support pressure pipes or pressure junctions. To runthe GVF-Rational solver on a model, the software internally converts pressure pipes and pressure junctions to conduits and manholes during calculation, respectively. To protect the original data, the pressure pipe and pressure junction elements are not changed in the model, only invisibly during GVF solver loading .

Pressure pipes are treated as circular conduits and are solved with Manning’s equation with the following rules applied to the converted conduit:

• The converted conduit has the same diameter as the pressure pipe.
• Pressure pipe roughness is converted to an equivalent conduit roughness value based on the pressure friction method and gravity friction method as follows:
• Manning's n = 1.3/C, where C is Hazen Williams C
• Manning's n = 0.0952/(|ln(e/7.4 + 0.000182)|), where e is Darcy Weisbach e
• Manning's n = Kutter's n
• Virtual pipes are treated as physical pipes, using the original data.
• Number of Barrels is set to 1.
• Design Conduit is set to False.

Pressure junctions are treated as manholes with the following rules applied to the converted manhole:

• Manhole diameter is set to zero.
• Manhole rim elevation is set to the highest crown elevation of connected pressure pipes.
• Manhole is set to Bolted.
• Manhole Design is set to False.