ND Journeyman Plumber common mistakes
ND Journeyman Plumber · Understand the traps and how to avoid them.
When a question cites a fixture-unit or sizing value, guessing from field habit instead of applying the code table the question names, so the answer reflects local practice rather than the adopted code edition.
Most candidates learned on the job under a local amendment or an older code cycle, and the exam tests the adopted model code as written. Field shortcuts become automatic and feel correct.
What to do instead
Before answering any sizing or fixture-unit item, write the governing table name and the edition on scratch paper, then look up the value mentally against that table rather than your memory of the job site. Build a one-page table of the most-tested values (fixture units per fixture, drainage and vent sizing, water-supply fixture-unit curves) and rehearse it until recall is table-based.
Treating a local amendment or inspector preference as the exam answer when the question is silent on jurisdiction.
Candidates with years of experience in one municipality assume their local rule is universal, and the exam deliberately tests the base code unless it states otherwise.
What to do instead
Adopt a rule: if the stem does not name a jurisdiction or amendment, answer from the model code. Flag mentally any item where your local rule differs, and practice those items separately so you can switch between the two deliberately.
Sizing a water-supply line from pipe diameter alone without converting the connected fixtures to demand in fixture units and applying the developed-length and pressure-loss factors.
Pipe sizing on service work is often done by rule of thumb, and candidates skip the intermediate conversion steps under time pressure.
What to do instead
Work every water-supply sizing item in the same fixed sequence: list fixtures, assign fixture units, sum with the demand curve, determine available pressure after static loss and friction, then read the size. Practice the sequence until it is automatic, and always check that the answer accounts for the longest run and elevation.
Confusing a vent's function with a drain's and installing or approving a wet vent, common vent, or vent size that does not satisfy the trap-arm distance and vent-size rules.
Vent and drain questions look similar on paper, and candidates who do mostly drain work underweight vent requirements.
What to do instead
For every venting item, first identify the trap it protects, then check trap-arm length against pipe diameter, then confirm vent size and connection height. Memorize the trap-arm distance table and the conditions under which wet venting is permitted, and redraw the DWV layout for each practice question before choosing.
Missing the slope requirement on horizontal drainage piping and picking a grade that is too steep or too shallow, or applying the wrong slope to a larger-diameter line.
Slope is often set by eye or by existing structure on the job, and candidates do not recall that the required grade changes with pipe size and that excessive slope is also a defect.
What to do instead
Memorize the standard grades by pipe diameter and the rule that slope must be uniform. On slope items, compute the fall over the stated run and compare with the required grade rather than estimating. Practice converting between percent grade, fraction, and inches per foot.
Answering fixture and faucet questions from product familiarity rather than the code's requirements for backflow protection, air gaps, and fixture clearance or installation dimensions.
Candidates know the products they install daily but have not memorized the protection requirements that attach to specific fixtures and connections.
What to do instead
Build a fixture-by-fixture table covering the required backflow protection, minimum air gap, and the clearance or spacing dimensions the code specifies. Review it before each study session and test yourself by naming the protection device required for each fixture type from memory.
Skipping the safety items on confined-space entry, trenching and shoring, and gas piping pressure testing because they seem like common sense.
Experienced candidates assume field habits satisfy the exam, but the exam tests specific thresholds such as trench depth requiring protection and the required test pressures and durations.
What to do instead
Treat safety as a memorization domain: learn the depth and slope thresholds for trench protection, the atmospheric testing and attendant requirements for confined spaces, and the gas-piping test pressure and hold time. Write these numbers on a single reference card and review it daily until they are exact.
Reading only the last line of a long scenario question and answering the wrong thing, or ignoring qualifiers such as EXCEPT, NOT, or BEST.
Exam stems are deliberately long and candidates under time pressure skim, and the qualifier often appears mid-stem rather than at the end.
What to do instead
Underline the qualifier and the actual question before reading the options. For EXCEPT and NOT items, evaluate each option as true or false against the stem and select the outlier rather than the first plausible answer. Practice with timed sets to build the habit of a deliberate read.
Leaving calculation items blank or rushing them, when fixture-unit sums, slope, and pressure conversions are mechanical and reliably earn points.
Candidates fear math under time pressure and either skip or guess, losing points on the most predictable items on the exam.
What to do instead
Drill the small set of recurring calculations until they take under a minute each: fixture-unit totals, fall over a run, psi to feet of head, and pipe volume. Show the setup on scratch paper even when the answer seems obvious, and never leave a calculation blank when an estimate can eliminate options.
Studying by rereading the code book cover to cover instead of targeting the high-frequency topics, so recall is broad but shallow on the items that actually appear.
The code is long and rereading feels productive, but it does not build the retrieval speed the exam requires.
What to do instead
Study from practice questions first, tag each miss by domain and by the specific table or rule involved, and reread only the sections those misses point to. Keep a running list of missed rules and re-test them weekly until each is answered correctly twice in a row.