Should I use the inside diameter or outside diameter for the "diameter" field for my pipes and conduits?
All of the OpenFlows products use the inside diameter (ID) for calculations. So, you should enter the inside diameter for each pipe's or conduit's "diameter" field.
Nominal Diameter for most common material types is close enough to Internal Diameter to be used directly for modelling. However, you should be careful for some materials, as the manufacturer's expressed "nominal diameter" may refer to the outside diameter, which could be substantially different from the inside diameter. Discrepancies in model calibration are usually related to errors in roughness coefficients, not diameters.
If needed, you can filter the pipe flex table based on material and globally change the nominal diameter (say 4 in.) to the internal diameter (say 3.97 in) for each pipe material.In most cases the difference between nominal and internal diameter is negligible. Some pipes like HDPE may have a notable difference.
To help avoid confusion when other users are reviewing the model, consider the following: