Most trade exams in the country are open book. You learn where things are, you tab the book, and on exam day you look them up. Texas plumbing is not that exam.
The Candidate Handbook is blunt about it: dictionaries, books, papers (including scratch paper) and reference materials are not permitted in the examination room. Pockets emptied, sleeves rolled up, phone in a locker. The administrator hands you note materials once you are seated, and they stay in the room.
So the skill the exam tests is not "can you find it." It is "do you know it." Here is how I would study for that.
1. Learn the number next to its rule, never alone
A list of bare numbers falls out of your head by Tuesday. "80 psi" means nothing on its own. "Static pressure above 80 psi needs a pressure-reducing valve" is a sentence you can picture: the gauge, the valve, the reason. Learn every number inside the sentence that gives it a job.
Then flip it. Cover the number, read the rule, say the number. Cover the rule, read the number, say the rule. If you can only do it one way, you do not have it yet.
2. Group by what the number does, not by chapter
Chapters are how the book is organised. Your memory is not organised that way. Group the distances together (15 inches to the wall, 30 center to center, 18 inches in front of a cleanout, 12 inches of cover on buried pipe). Group the slopes together (1/4 inch per foot on small drains, 1/8 inch per foot on condensate, 1/4 inch in 15 feet on wet gas). Group the test pressures together (10-foot head or 5 psi for 15 minutes on drainage, 50 psi for 15 minutes on water).
When two rules share a number, learn them as a pair. When two rules that feel similar carry different numbers, learn them as a contrast: the atmospheric vacuum breaker sits 6 inches above the flood-level rim, the pressure vacuum breaker 12 inches.
3. Let the misses schedule your review
You will forget things. That is not a problem; it is the information you need. The section you miss today is the one to see again tomorrow, and again in three days, and again in a week. The section you get right three times in a row can wait a month.
This is what a weak-area drill does automatically, and it is the single most efficient use of study time on a memory exam, because it spends your minutes on what you do not know instead of on what you enjoy.
4. Practise with nothing open
Once a week, take a full mock with the clock running and the book closed. Not "I will just check this one thing." Closed. The point is not the score; it is to find out which numbers are actually in your head and which ones you were quietly looking up without noticing.
The first time is humbling. The third time, you notice the numbers arriving before you finish reading the question. That is the feeling you want on exam day.
5. Do not memorise the differences between the codes
Texas adopts both the 2018 UPC and the 2018 IPC, and the exam is written to be passable from either. Where the two books disagree, a fair question cannot be written, so those values are the ones you can stop carrying. Learn the shared rules; they are the exam.
6. The law is numbers too
The Plumbing License Law and Board Rules are on the exam, and the handbook names the sections. They carry their own numbers: 8,000 hours and a 48-hour course for the Journeyman, 6 hours of continuing education a year with 3 in health and conservation, a license expired 90 days or less renewed at 1-1/2 times the fee, $5,000 a day as the top administrative penalty, 30 days to report a name or address change. Same method. Number next to rule, cover, recall.
The whole method in one line
Number next to rule, grouped by job, reviewed on the schedule your misses set, tested with the book closed. Do that for a few weeks and the exam room stops feeling empty.
If you want to know where you stand right now, the free 20-question exam takes about twenty minutes and shows the section numbers for every answer, in both codes.