If you are studying for a test you need to ensure that your study material covers the code the test is based on. If you study a book based on the IPC and the test is based on the UPC you will most likely fail. In fifteen years you should have gained a great deal of the local plumbing requirements. Not sure about your state but here in hawaii before you can take the journeyman test you need time in the trade (10,000 hours). Additionally, your employer needs to itemize your work experience by job catagories (rough-in waste and water, setting fixtures, pipe hangers and support, repairs, ect.) If your experience doesn't sufficiently cover the spectrum of the trade (according to a board), your application will be denied. Do you have knowledge of the local code book? When I was getting ready to take the journeyman test I purchased a study book from the same company that prints the codebook that explained the intent of each item in the codebook. What code does your state use? Additionally, if you contact the agency that gives the test they will reccomend study materials.