Please correct me if I am wrong, but to save others some time with the same problem let me point out that the link you provided doesn't address adding new records, e.g. adding other lines for PVC pipe as an example. It shows how to modify the existing records. The references to adding are simply refering to adding information about the pipe that is mot there. The only reference to address my question is the second to last comment that points you to an API and there is really no direction provided... not exactly the most user friendly approach.
I hope Autodesk can improve the pressure pipe capaibilites of the software... in the meantime I need to move forward by modifying the ductile iron pipe entries to make them PVC...
Thanks for the feedback.