Yes you can add any part size to the part catalog, only remember that one should back up the entire part catalog folder to a SAFE place prior to entering the Part Builder.
I would suggest creating a part family using the PVC pipes, then change the MATERIAL description, beware that IF the material description isn't S T R E T C H E D open as wide as what you intend to type into that field it will truncate it and you will wind up with a weird material description in you drop down list evermore.