Code navigation drills

Luis timed Maya with his phone. "Minimum size of a building drain serving a single water closet. Go." She knew the answer from the job, but he made her find it in the book anyway, and it took her almost three minutes: she started in the wrong chapter, found the right table, then went back to check the footnotes. "On the job, three minutes is nothing," he said. "On the exam, you have a little over two minutes per question, and some questions need two or three lookups. Finding things fast is not a trick. It's most of the exam."

This lesson is a set of drills. It gives a method for finding any requirement in the plumbing code, a set of practice lookups grouped by type, and a way to time and track your speed so that you can see it improve. The goal is that every common lookup becomes a habit: the first place you look is the right place.

How a plumbing code is built

Every plumbing code has a structure, and learning the structure is the first drill. The International Plumbing Code, and the Ohio Plumbing Code based on it, is organized in chapters that follow the path of water through a building: administration, definitions, general regulations, fixtures, water heaters, water supply and distribution, sanitary drainage, indirect and special waste, vents, traps and interceptors, storm drainage, special piping systems, nonpotable water systems and referenced standards, followed by appendices. Within each chapter, sections are numbered with the chapter first, so section 906 is in Chapter 9 and Table 906.1 is the table that section uses. Tables sit next to the rule that tells you how to apply them.

Maya made a one-page map of the code's structure and kept it in the front of her notebook. It listed each section or chapter, its main subjects and its most-used tables. For the first two weeks, she looked at the map before every lookup. By the third week, she no longer needed it.

The five-step lookup

Luis taught her a method that turned searching into a routine. It has five steps, and skipping any of them is where most lookup errors come from.

• Pick the key word. Every question has one or two words that decide where the answer lives: a fixture, a pipe type, a system, a test. In "What is the minimum trap size for a floor drain?", the key words are trap and floor drain.
• Check the definition. If the key word is a defined term, read the definition. The exam uses defined terms exactly. A branch is not a stack, a fixture drain is not a trap arm in every code, and a building drain stops where the building sewer begins.
• Find the section. Use the structure map or the index to go to the right section. The index is alphabetical and lists many terms under the system they belong to, so try both the specific word and the system.
• Read the table or the rule. Read the column headings and the units first, then find the row. Check whether the table gives a maximum or a minimum, and whether values are per fixture, per branch or per stack.
• Check footnotes and exceptions. Many rules have exceptions in the next sentence, and many tables have footnotes that change the value for one case. Read them every time, even when you are sure.

The fifth step is the one most candidates skip, and the exam writers know it. A common question pattern gives a situation that falls into an exception, with the general rule as one of the wrong options. A candidate who stops at the general rule picks the distractor.

Drill set 1: definitions

Definitions in Chapter 2 are the fastest points on the exam and the most common source of avoidable errors. Maya drilled them with flash cards: the term on the front, the definition and an example on the back. She worked through the defined terms that come up most in plumbing questions until she could explain each in one sentence and find it in the book in under twenty seconds.

A good definition drill has three questions for each term: what it is, what it is not, and one example on a real job. Maya added a fourth after a practice test: where does it stop? Many errors came from not knowing the boundary between a fixture drain and a branch, or between a building drain and a building sewer.

Drill set 2: tables

Tables hold most of the numbers on the exam. Maya drilled each of the main tables with three types of question: a direct lookup, a reverse lookup and a combined lookup. She timed every drill and wrote the time on the card.

• Direct lookup: given the input, find the value. What is the fixture unit value of a bathtub?
• Reverse lookup: given a value, find the input. What is the smallest stack that can carry a given number of fixture units?
• Combined lookup: two tables or a table and a rule. How many fixture units does a group of fixtures produce, and what size branch carries them?

The reverse lookup is where most mistakes happen. When a table lists the maximum load for each size, the answer to "what size is needed" is the first size whose maximum is equal to or greater than the load, not the size whose maximum is closest to the load. A load of 21 fixture units on a branch table that allows 20 for one size and 160 for the next needs the larger size, even though 21 is much closer to 20.

Drill set 3: rules and exceptions

The third drill is for rules that are written as sentences rather than tables: where a cleanout is required, how far a trap may be from its vent, when an air admittance valve may be used, which fittings may change direction. For each rule, Maya wrote a card with the rule on one side and the exception on the other. Then she wrote one exam-style question that tested the exception rather than the rule.

Luis's favorite exam pattern was what he called the almost-rule question. The question describes a situation that is almost the common case but differs in one detail, such as a pipe size, a vertical rather than horizontal direction, or a fixture that is not a water closet. The wrong options include the answer for the common case. The only defense is to read the question for the detail and to read the rule to the end.

Speed tools: the index, the tabs and the table of contents

On the F25, the book is the tool, and three parts of it carry the speed: the tabs, the index and each chapter's table of contents. Maya used the tabs for tables she knew she would need, the index for words she could not place, and the chapter contents for anything in between. She practiced by covering the answer options, finding the answer in the book, writing it down, and only then uncovering the options. That stopped the options from steering her toward a familiar but wrong number.

A useful drill is the reverse question: open the code at a random table, and write a question that the table answers. It builds familiarity with tables you might otherwise skip, and it shows how the exam writers think, because that is exactly how they work.

Timing and tracking

Drills only improve speed if speed is measured. Maya logged every lookup: the date, the type of lookup, the time in seconds and whether she got it right. Each week, she worked out her average time and her accuracy for each type. Luis set targets: definitions under 30 seconds, direct table lookups under 45 seconds, combined lookups under 2 minutes, all with at least 90 percent accuracy.

The program below takes a drill log, computes the average time and accuracy by drill type each week, and flags any type that misses its target. Maya ran it every Sunday evening and used the flags to choose the next week's drills.

# Code navigation drill log: weekly average time and accuracy by type
log = [  # (week, type, seconds, correct)
    (1, "definition", 48, True), (1, "definition", 35, True), (1, "definition", 62, False),
    (1, "direct", 70, True), (1, "direct", 95, True), (1, "direct", 58, False),
    (1, "combined", 190, True), (1, "combined", 240, False), (1, "combined", 165, True),
    (4, "definition", 22, True), (4, "definition", 18, True), (4, "definition", 31, True),
    (4, "direct", 41, True), (4, "direct", 38, True), (4, "direct", 52, True),
    (4, "combined", 110, True), (4, "combined", 98, True), (4, "combined", 131, False),
]
targets = {"definition": 30, "direct": 45, "combined": 120}   # seconds
for week in sorted({w for w, *_ in log}):
    print(f"Week {week}")
    for kind, target in targets.items():
        rows = [(s, c) for w, k, s, c in log if w == week and k == kind]
        avg = sum(s for s, _ in rows) / len(rows)
        acc = 100 * sum(c for _, c in rows) / len(rows)
        ok = "on target" if avg <= target and acc >= 90 else "DRILL MORE"
        print(f"  {kind:10s} avg {avg:6.1f} s (target {target:3d})  accuracy {acc:5.1f} %  {ok}")

Week 1
  definition avg   48.3 s (target  30)  accuracy  66.7 %  DRILL MORE
  direct     avg   74.3 s (target  45)  accuracy  66.7 %  DRILL MORE
  combined   avg  198.3 s (target 120)  accuracy  66.7 %  DRILL MORE
Week 4
  definition avg   23.7 s (target  30)  accuracy 100.0 %  on target
  direct     avg   43.7 s (target  45)  accuracy 100.0 %  on target
  combined   avg  113.0 s (target 120)  accuracy  66.7 %  DRILL MORE

In the sample log, week 4 meets the time targets for all three types, but combined lookups are still below 90 percent accuracy, so the program flags them. Speed without accuracy is no improvement. Maya's response was to slow down on combined lookups and add the footnote check back in, which brought accuracy up within two weeks without losing much time.

A twenty-minute daily drill

Luis's daily drill took twenty minutes and had four parts. Maya did it at lunch on work days, with a timer running.

After six weeks, Maya's lookups were fast enough that she started to see the structure of questions before she read the options: "this is a combined lookup with a footnote" or "this is a definition question disguised as a sizing question". That recognition is the real goal of drilling. It lets you spend the time saved on the questions that need thought.