BOABC Plumbing Level I common mistakes
BOABC Plumbing Level I · Understand the traps and how to avoid them.
Answering code questions from memory of how a job was done in the field rather than from the adopted code text, so the answer reflects a local habit instead of the code requirement.
Experienced tradespeople and inspectors rely on routine and jurisdiction custom; the exam tests the adopted model code and its amendments, which often differ from field shorthand.
What to do instead
For every code question, restate the requirement in code language before choosing an answer, and flag any option that matches 'how we always do it' as suspect until verified against the code concept being tested.
Treating local amendments and the model code as interchangeable, picking the model-code value when the question describes a jurisdiction with a stricter amendment.
Candidates study one code book and skim the amendment list, assuming amendments are minor; in practice amendments frequently change setback, sizing, and permit thresholds.
What to do instead
Build a one-page comparison of the model code versus the local amendment set for the jurisdiction named in the exam scope, and practice identifying which document governs when a question mentions the authority having jurisdiction.
Confusing the roles of the permit applicant, the design professional, and the authority having jurisdiction when a question asks who is responsible for a submission or correction.
In real projects these duties blur because one person often performs several roles; the exam tests the formal allocation of responsibility in the permitting process.
What to do instead
Map each plan-review task to its responsible party in a short table (applicant, designer, plan reviewer, inspector) and drill questions by asking 'who signs or approves this step' before reading the options.
Reviewing a plan set fixture by fixture and missing cross-sheet inconsistencies such as a drain size on the isometric that contradicts the schedule or the riser diagram.
Candidates read sheets in order rather than by system, so related information on non-adjacent sheets is never compared.
What to do instead
Adopt a system-by-system review pass (water supply, drainage, venting, fixtures) that traces each system across plan, riser, and schedule sheets, and note every discrepancy before judging code compliance.
Accepting a stated pipe size or slope on the plan without checking whether the connected fixture load and developed length actually support it.
Reviewers focus on whether a number is present rather than whether it is correct; sizing and slope calculations are the most calculation-heavy part of plan review.
What to do instead
Recompute at least one sizing and one slope check per practice plan set, using the fixture-unit and developed-length tables, and write the calculation next to the plan value so mismatches become obvious.
Writing inspection findings as general opinions ('plumbing looks acceptable') instead of citing the specific code section and the exact observed condition.
Field inspection experience teaches verbal, informal communication; written documentation standards are rarely practiced on the job.
What to do instead
Practice drafting findings in a fixed three-part format: observed condition, code citation, required corrective action, and apply it to at least ten sample scenarios until the format is automatic.
Skipping the test or verification step in an inspection sequence, approving a drain or water line on visual inspection alone when the code requires a pressure or flow test.
Visual checks are fast and familiar, while test procedures require setup and waiting; under time pressure candidates describe the visual pass and omit the test.
What to do instead
Memorize the required test type, pressure or head, and duration for water supply, drainage, and venting systems, and rehearse inspection sequences as ordered checklists that always end with the test and its result.
Choosing an answer that resolves a conflict by ignoring the stricter requirement, for example approving work because the owner accepted the risk or because the contractor is certified.
Candidates import workplace pragmatism, where certification, seniority, or owner consent often ends a disagreement, into an exam that tests rule hierarchy.
What to do instead
When two requirements conflict, apply the rule that the more stringent provision governs and that owner agreement cannot waive a code minimum; drill conflict scenarios until this hierarchy is the default response.
Failing to disclose a conflict of interest, such as inspecting or reviewing work by a relative, employer, or business partner, and proceeding as if the relationship were irrelevant.
Small jurisdictions and family trades make overlapping relationships common, and candidates underestimate how strictly the exam treats even perceived conflicts.
What to do instead
Memorize the disclosure-and-recusal sequence (identify, disclose in writing, withdraw from the decision) and apply it to every scenario involving a personal, financial, or employment relationship.
Misjudging the scope of inspector authority, for example ordering work beyond the code, waiving a required permit, or issuing a stop-work order without the documented basis.
Authority varies by jurisdiction and candidates generalize from one employer's practice; the exam tests the limits of administrative power, not its typical use.
What to do instead
Study the administrative provisions on permits, notices, stop-work orders, and appeals, and for each scenario ask whether the action is authorized, required, or prohibited before selecting an answer.