Every week someone asks me the same thing: "I learned on the UPC, but my buddy says the Texas exam is written to the IPC. Do I have to start over?"
No. And the reason is worth understanding, because it changes how you study.
Texas adopts both books
Board Rule 367.2(a) adopts the 2018 Uniform Plumbing Code and the 2018 International Plumbing Code (with the codes it incorporates, including the 2018 International Fuel Gas Code). A licensee working in an unincorporated area with no local code installs to whichever of the two the Board adopted. A city picks one for its own ordinance. The Candidate Handbook says it plainly: study the Plumbing License Law, the Board Rules, and either the 2018 IPC with the 2018 IFGC or the 2018 UPC. The exam is written to be passable from either one.What a two-code exam can honestly ask
Think about what that means for the person writing the questions. If the UPC says one number and the IPC says another, a question about that number has two right answers depending on which book you own. The exam cannot ask it. So the questions land on the rules the two codes share.
And they share most of them. Both books were written from the same industry standards (ASSE, ASME, AWWA, NSF), so the backflow devices, the air gaps, the fixture unit values, the trap seal depth, the drain slope, the water heater relief valve, the gas piping supports and the combustion air rules line up almost everywhere.
A few examples of shared rules, with both citations:
- Static pressure above 80 psi needs a pressure-reducing valve (UPC 608.2 / IPC 604.8).
- A fixture trap holds a seal of 2 to 4 inches (UPC 1005.1 / IPC 1002.4).
- A water closet sits at least 15 inches from a side wall and 30 inches center to center (UPC 402.5 / IPC 405.3.1).
- Horizontal drains 2 inches and smaller slope 1/4 inch per foot (UPC 708.1 / IPC 704.1).
- The water heater pressure relief valve is set no higher than 150 psi (UPC 608.4 / IPC 504.5).
Where the books disagree, and why you can relax about it
They do disagree in places. The maximum hot water temperature at a public lavatory, the depth of a building drain below grade, the trap arm length tables, whether air admittance valves are allowed at all, the gas piping test pressure. A fair exam stays away from those, because a fair exam has one right answer.
So when you find one of these differences in your studying, the move is not to memorise both values. The move is to note that this is a difference, so you recognise it if a study guide or a coworker brings it up, and then spend your time on the shared rules that can actually be asked.Every lesson on this site ends with a short list of exactly those differences for that chapter, with both citations. We do not write questions on them. That is the whole point.
What to do with the book you already own
Keep it. Learn it well. The chapter structure differs (the UPC puts fuel gas in chapter 12, the IPC hands it to the IFGC; the UPC puts vents in chapter 9 and traps in chapter 10, the IPC does the same), but the rules inside are what the exam draws from, not the chapter numbers.
Then check yourself against questions that show both citations, so you see the other book's section number next to the one you know. After a week of that, "UPC or IPC" stops being a question. You are studying plumbing, and both books agree on what that is.
If you want to see where you stand, the free 20-question exam takes twenty minutes and every answer shows both section numbers.