Hi Jim,
In order to add Pipe Sizes in Pressure Network, you have to do it in the Content Catalog Editor. Open the Default Catalog that you were using (see Catalog Database File:) which is in .sqlite format in the Content Catalog Editor and browse the Pipes and add sizes that you want. For the Pipe Fittings, you have to model it first the geometry in 3D Solid every sizes that you need. I usually do this in Inventor and export it in dwg file. You have to put '_AUTODESKCONNECTIONPOINT" in every connection of your fittings. After putting insertion point, export them using "PUBLISHPARTCONTENT" and import them in your Content Catlogue Editor where you put all the parameters in it.