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The full 306A bank is 130 questions across six topic areas, weighted the way the trade is. What each area holds, and what apprentices keep getting wrong in it:
DWV Systems — 34 questions. The biggest block, and where the most marks move: fixture unit loading, trap arm length, developed length of a vent, grade on horizontal drainage, cleanout placement, and telling a wet vent, a circuit vent and an individual vent apart by function. The error we see most is treating trap seal loss as one problem — apprentices name siphonage and stop, when back pressure, evaporation, capillary action and wind effect all end with a dry trap and each has a different fix. The second is reading a fixture unit table for the fixture instead of the cumulative load on the branch.
Water Supply — 25 questions. Sizing the water service and distribution, static head and working pressure, friction loss, backflow prevention, expansion control, and hot water recirculation. Friction loss is the reliable trap: apprentices work from the measured pipe run and forget the equivalent length every elbow, tee and valve adds, so the answer comes out one pipe size light. Backflow catches people too — the device follows the hazard rating and whether the connection sits under continuous pressure, not pipe size.
Fixtures — 18 questions. Rough-in dimensions, fixture carriers, flushometer and tank operation, trap and tailpiece sizing, clearances for accessible fixtures, and servicing bowl and tank assemblies. This area rewards anyone who has actually set fixtures. The usual loss is rough-in heights and clearance around a water closet, which many apprentices know as "whatever the last job used" rather than as a dimension they can state.
Code & Inspection — 20 questions. Test and inspection procedure: what gets tested, at what pressure, for how long, and what has to stay exposed when the inspector arrives. Plus permits, re-inspection, and working a code table through to a defensible answer. The mistake is memorising a value and never learning the route to it — editions change and provinces amend, so what is worth practising is the lookup.
Safety & Tools — 16 questions. Confined space entry, trenching and shoring, hot work, PPE selection, WHMIS labelling, and safe use of press tools, torches, drain machines and powder-actuated fasteners. Most apprentices score well here and then give back the trenching questions, where required protection follows soil type and depth, not crew habit.
Gas Piping — 17 questions. Sizing gas pipe from connected load and developed length, appliance venting categories, combustion air, shut-off valve and drip leg placement, and leak testing. The common error is sizing from load alone and skipping the developed-length step; the other is mixing up venting categories, which decide vent material and slope. Note that gas fitting is licensed separately in most provinces — these questions cover overlapping piping knowledge, not a substitute for a gas ticket.
Sit it timed, in one block, with nothing open — the first pass exists to show what you know cold. Put a dot beside every question you guessed at, including the ones you feel good about.
Score it twice: the number you got wrong, and the number you got right with a dot beside it. Those lucky ones flip to misses on a bad morning, so they belong in the study pile too. Sort by topic and see where it clusters.
With the 306A mix, the cluster tells you what to do next. Misses bunched in DWV Systems and Water Supply are sizing and load problems; the fix is worked examples with the table in front of you, not re-reading theory. Code & Inspection misses are the opposite — practise finding the answer in the code book against a clock, because navigation is the skill being tested. Gas Piping and Safety misses are isolated facts; flashcards handle those. Sit the same 50 a week later and treat anything still wrong as a real gap.
This mock exam is a 50-question slice. The 306A Complete Question Bank has all 130 questions with a full explanation for every answer, organized by the published occupational standard topic areas, in one printable offline PDF.
Get the 306A Question Bank — CA$24 →Before planning study time, read the published examination weightings for the Plumber trade. On the Plumber examination weightings page, the interprovincial exam is described as 125 questions over seven Major Work Activities, the largest share — 26% — going to sewers, sewage treatment systems and DWV, and 19% to water service and distribution. The Red Seal exam preparation guide gives the format as multiple choice, four options, one correct answer worth one mark, four hours' writing time, and a pass mark of 70%. Provincial and territorial authorities administer the exam, so confirm the specifics where you are challenging it.
Our bank follows that emphasis rather than spreading questions evenly — DWV is the largest block here for the same reason it is the largest there. The mapping is not one to one: the published standard gives low-pressure steam, hydronics and specialized systems their own activities, and our Code & Inspection group cuts across several. Treat the published weightings as the authority and this bank as practice measured against them.
Is the free set a sample of the paid one? Yes — a 50-question slice of the same 130-question bank in the same topic proportions, so about a quarter is DWV. The full bank adds the other 85, each explained.
Do I need my code book? For most questions, no. For the Code & Inspection questions and the DWV sizing ones, work them with your provincial plumbing code open, because the skill being built there is the lookup itself.
Is it current with the latest code edition? The questions test principles, procedures and how to reason through a table rather than specific published values, because editions and provincial amendments differ. Confirm exact numbers against your adopted edition.
I work commercial — is this too residential? It stays with fundamentals shared by both: fixture unit loading, venting method, backflow protection, test procedure. Process piping, medical gas and large hydronic work sit outside a 130-question bank's depth.
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