What is on the 306A Plumber Red Seal exam.

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01What is the 306A Plumber Red Seal exam?

It is the national certification exam for the trade that the Red Seal Program calls Plumber. Twelve provinces and territories use that title; Quebec calls the trade Pipe Fitter (Plumber). 306A is Ontario's trade code for it. You will also see it called the Red Seal plumbing exam, the interprovincial (IP) exam or, in Ontario, the certifying or C of Q exam. In Ontario these all name the same sitting: one interprovincial Red Seal exam, and passing it earns the Certificate of Qualification with the Red Seal endorsement.

The content is set nationally. According to the Red Seal Exam Preparation Guide, tradespeople from across Canada decide what goes into the trade's Red Seal Occupational Standard (RSOS), write and review every exam question, and decide how many questions each section gets. The exam is then administered by the provincial and territorial apprenticeship and certification authorities; in Ontario that is Skilled Trades Ontario.

The format is the same as every Red Seal exam: multiple choice, four options (A to D), one correct answer, one mark per question and no penalty for a wrong answer. The Plumber exam has 125 questions and the writing time is four hours, about 1 minute 55 seconds per question. The pass mark is 70 per cent. Seventy per cent of 125 is 87.5, so you need 88 correct answers and can miss 37.

The standard behind the exam is the 2023 Red Seal Occupational Standard for Plumber (catalogue number Em15-3/6-2023E). The Red Seal trade page points to it as the basis of the exams and carries no note about an older edition, and the exam information page and the Self-Assessment Guide give the 125-question breakdown in its task numbering. The preparation guide stresses that the exam covers the trade across Canada at the journeyperson level, not only the work you do: a residential service plumber will still see sewage treatment, hydronic, process piping and medical gas questions.

02What is on the 306A exam?

The Red Seal Program publishes how many questions come from each major work activity. For Plumber the 125 questions break down like this.

Drainage and water carry the exam. Block C, sewers, sewage treatment and DWV, is the heaviest at 32 questions (25.6 per cent), and Block D, water service and distribution, is next at 24 (19.2 per cent). Together they are 56 of the 125 questions, 44.8 per cent. Blocks E and F follow at 17 and 16, then A at 14 and B at 13. The lightest is G, specialized systems, at 9 (7.2 per cent). The shares here are worked out from the question counts. The Self-Assessment Guide rounds them to 11, 10, 26, 19, 13, 13 and 8 per cent; the question counts are the figures to rely on.

03What does each block cover?

The task names below are the ones the 2023 standard lists under each major work activity, with the number of questions the Red Seal Program assigns to each. The standard has 21 tasks and 95 sub-tasks, and questions are written to the sub-tasks. Three tasks carry no questions: communication and mentoring (A-5), and the two that are not common core, low-pressure steam (F-16) and potable water fire protection (G-20). The preparation guide's rule is that a sub-task performed in fewer than 70 per cent of provinces and territories is not tested. That leaves 85 sub-tasks under 18 tasks. The largest single task is interior DWV (C-10) with 20 questions, then potable water distribution (D-12) with 12 and plumbing fixtures and appliances (E-14) with 11.

Block A: Common occupational skills (14 questions)

Five tasks. Performs safety-related functions (3 questions) covers the work environment, PPE and lock-out and tag-out (LOTO). Uses and maintains tools and equipment (3) covers common and access equipment, rigging and crane loads, welding, and soldering and brazing. Organizes work (3) covers project tasks, materials and documentation. Performs routine trade activities (5), the largest, covers piping layout and length calculations, supports and sleeves, commissioning, protecting piping, trench excavation and fire stopping. Uses communication and mentoring techniques carries 0 questions.

Block B: Preparing and assembling tube, tubing and pipe (13 questions)

Two tasks. Prepares tube, tubing and pipe (6 questions) covers inspecting, cutting, bending and preparing connections by reaming, threading and grooving. Joins tube, tubing and pipe (7) has one sub-task per material (copper, plastic, steel, cast iron, and specialized pipe such as glass).

Block C: Sewers, sewage treatment and DWV systems (32 questions)

The heaviest block, a quarter of the exam. Installs, tests and services sewers (7 questions) covers sanitary, storm and combined sewers: sizing from hydraulic load and grade, maintenance holes and catch basins, and hydrostatic, smoke and air, and mandrel tests. Installs, tests and services sewage treatment systems (5) runs from septic and holding tanks and leaching beds, planned from soil tests and the daily volume of sewage, to lagoons and treatment plants; some jurisdictions require additional certification for it. Installs, tests and services interior drainage, waste and vent (DWV) systems (20) is the single largest task on the exam, about one question in six. Sizing runs through it: the standard has you calculate the building's total hydraulic load from the tables in the codes, then size the sanitary drainage with its vent piping, and the storm drainage from the roofs and paved areas it serves. The tests are hydrostatic and pneumatic pressure tests and a final smoke or 25 mm water column test.

Block D: Water service and distribution (24 questions)

Installs, tests and services water service (6 questions) runs from the municipal or private supply into the building, sized from fixture units, developed length, elevation, pressure and velocity, with thrust blocks, mechanical restraints and tie rods to hold it. Installs, tests and services potable water distribution systems (12) adds friction loss to the sizing, covers pressure-reducing valves, water heaters, tempering valves and shock arrestors, and gives cross connection control a sub-task of its own: reduced pressure backflow preventers, double check valve assemblies, air gaps and the rest, to standards such as CSA B64.10. Installs, tests and services private water pressure systems (6) covers wells, cisterns and surface sources, jet, submersible and booster pumps and pressure tanks, with Boyle's law and total dynamic head among its formulas.

Block E: Fixtures, appliances and water treatment (17 questions)

Two tasks. Installs, tests and services plumbing fixtures and appliances (11 questions) covers fixture supports and carriers, the fixtures themselves, appliances such as water heaters and dishwashers, and water-saving trim, then testing and servicing them. Installs, tests and services water treatment systems (6) starts with sizing from a water test (hardness, pH, total dissolved solids) and covers filtering, softening, UV, reverse osmosis and neutralizing.

Block F: Low-pressure steam and hydronic systems (16 questions)

Installs, tests and services low-pressure steam systems is not common core and carries 0 questions, so all 16 questions in this block are hydronic. Installs, tests and services piping and components for hydronic systems (9) covers piping designs from one-pipe to four-pipe and primary/secondary, air removal, expansion tanks, circulators, terminal units, controls and glycol. Installs, tests and services hydronic heating and cooling equipment (7) covers high and low mass boilers and their trim, such as low water cut-offs and relief devices, heat pumps and solar thermal panels, and on the cooling side chillers and cooling towers.

Block G: Specialized systems (9 questions)

Installs, tests and services process piping systems (5 questions) covers piping for food processing, high purity water, treatment plants and laboratories. Installs, tests and services potable water fire protection systems is not common core and carries 0 questions. Installs, tests and services other specialized systems (4) covers compressed air, natural gas and propane, medical gas and vacuum, radon mitigation, irrigation, ground source loops, solar thermal and rainwater harvesting. For fuel gas, the standard says plumbers install the piping from the point of supply to the appliance isolation valve, depending on provincial regulations.

04What kind of questions are they?

The Red Seal Program describes the Plumber question mix as knowledge and recall 15 to 25 per cent, procedural and application 60 to 70 per cent and critical thinking 10 to 20 per cent. On 125 questions that is roughly 19 to 31 recall questions, 75 to 88 procedural and 13 to 25 critical thinking. The procedural share ties Construction Electrician (309A) and is higher than the other pipe trades we cover (Steamfitter/Pipefitter 45 to 55, Refrigeration and Air Conditioning Mechanic 50 to 60); only Carpenter (403A) and Hairstylist (332A), at 75 to 85, go higher.

The exam information page gives one example of each type. The recall example asks where a pressure sensor sits in a medical gas system. The procedural example asks how to restrain an underground water service where thrust blocks cannot be used. The critical thinking example asks why the relief valve on a reduced pressure (RP) backflow preventer discharges on and off, which you work out from how the device should behave.

The Red Seal Exam Preparation Guide says procedural questions might include calculations, interpretations of diagrams or code books, and that questions will not say when they rely on the code. In this trade that means method: sizing drainage and vent piping from a hydraulic load, working out grade, choosing a cross connection control, and setting up a well pump and pressure tank. There are no trick questions, but the incorrect options are not always obvious.

05What do you get in the exam room?

The Red Seal Exam Preparation Guide lists what you are provided with: an exam booklet, a diagram booklet if required, a pencil and eraser, a calculator if needed, a bubble sheet and scrap paper, plus an acronym list, math formulas and code book information "if required".

For Plumber the exam information page publishes a formula sheet and an acronym list, both provided with the sitting. The sheet gives six constants (π = 3.1416; 1 ft² of equivalent direct radiation = 240 Btuh; 1 US gallon = 8.33 lb; 12 000 BTU of cooling = 1 ton; 0.433 psi per foot of head; 1.414 for a 45° offset), expansion coefficients for six pipe materials, metric to imperial conversions, and formulas for Boyle's and Charles' laws, expansion (L × ΔT × α), force, gpm, grade, softener grains, storm water from area and rainfall intensity, Watt's law and pressure, the hydronic Btuh = gpm × 500 × ΔT, and areas and volumes.

It has no fixture unit, hydraulic load or pipe sizing tables, and the page lists no code book information. The acronym list covers terms such as DWV, NPC, RP, DCVA, PRV, T&P, LWCO and the pipe materials; it gives you the meaning, not what the thing does.

No materials, bags, phones, watches or personal calculators are allowed. Ask your provincial or territorial office about anything else, including whether a code extract comes with the exam where you write. More on the day itself is in what to expect on exam day.

06Where does the plumbing code come in?

Everywhere in blocks C and D. The standard says plumbers use the National Plumbing Code (NPC) to ensure compliance, that changes to the NPC occur periodically, and that sizing is done according to codes and the authority having jurisdiction (AHJ): the total hydraulic load of a building is calculated "according to tables in codes". The preparation guide adds that if a trade has a code book, the Red Seal exam will reference the national code book, and that questions will not say explicitly that they refer to code.

Provinces adopt plumbing rules in their own way. In Ontario the rules are in Part 7 of the Ontario Building Code (OBC), and Skilled Trades Ontario's 2018 curriculum teaches Part 7 from Level 1, including which code Part 7 is based on. At Level 3 the same curriculum has a module on the National Plumbing Code that asks apprentices to identify the examination based on the NPC and the differences between the OBC and the NPC. Other provinces adopt the NPC, some with amendments, and British Columbia publishes its own plumbing code. Your apprenticeship authority can tell you which edition is in force where you work.

For the exam, that points to principles over clause numbers. The same exam is written in every province, so what carries across is the method: how fixture units and hydraulic load drive pipe size, how grade, trap arms and venting protect trap seals, where cleanouts and backwater valves go, which cross connection control suits which hazard, and how DWV and water systems are tested. If you trained on a provincial code, learn where it differs from the NPC, and practise finding things in the national code book until you are comfortable with its layout, as the preparation guide suggests.

07Plumber, steamfitter or gasfitter: which exam is yours?

The standard itself recognizes overlaps between plumbers and gasfitters, steamfitters/pipefitters, refrigeration and air conditioning mechanics and sprinkler fitters. The overlaps show on the exam: plumbers have a hydronic block, a low-pressure steam task (not tested), process piping, and fuel gas and medical gas under specialized systems. But each trade has its own standard and its own exam, and the one you write is the one for the trade you apprenticed in or are qualified to challenge.

Plumber (306A in Ontario) centres on drainage, water supply, fixtures and hydronics. Steamfitter (307A in Ontario, Steamfitter/Pipefitter on the Red Seal) is a separate compulsory trade with its own 130-question exam built around piping installation, low and high pressure steam, process piping and rigging; see the 307A Steamfitter exam guide. Potable water fire protection is not common core for plumbers, and the standard notes that the scope of that work is set by each jurisdiction.

Gas is a separate credential. The standard lists gas licensing among the additional credentials outside its own topic list, and says plumbers install gas piping from the point of supply to the appliance isolation valve where provincial rules allow. Skilled Trades Ontario's curriculum covers natural gas piping at Level 3, including the certification steps for gas-fitting licences, but the plumber Certificate of Qualification is not one of them. In Ontario the G3 and G2 gas technician certificates are issued separately by the Technical Standards and Safety Authority (TSSA), with their own exams. A Red Seal plumber who wants to connect gas appliances needs that licence as well; passing the plumbing exam does not give it.

08How do you become a Red Seal plumber in Ontario?

Plumber is a compulsory trade in Ontario. Skilled Trades Ontario says that to work in it you must hold a Registered Training Agreement, a Provisional Certificate of Qualification or a Certificate of Qualification and appear on its Public Register, and that a Certificate of Qualification in this trade must be renewed to stay valid.

Skilled Trades Ontario sets the apprenticeship at 9,000 hours, approximately five years: 8,280 on the job and 720 in school over three levels, with Grade 10 as the entry level in its 2025 trade report. Finishing earns a Certificate of Apprenticeship; passing the certifying exam, the Red Seal exam, earns the Certificate of Qualification. Skilled Trades Ontario issued 838 Plumber Certificates of Qualification in 2025. Experienced workers without an Ontario apprenticeship use its Trade Equivalency Assessment; see how to challenge the Red Seal exam.

As for the highest level, the Certificate of Qualification with the Red Seal endorsement is the journeyperson credential, and the standard describes no rank above it. With experience, it says, plumbers may become mentors, instructors, inspectors, estimators or project managers. See what is a Red Seal.

Elsewhere, each province and territory administers the exam and sets eligibility, fees and rewrite rules. See the Ontario Red Seal exam guide, Alberta, British Columbia, Saskatchewan, Manitoba or the guides by province, compare Red Seal exam fees by province, and read what happens if you fail the Red Seal exam before you book.

09How hard is the Red Seal plumbing exam?

It is demanding in three ways. First, it is procedural: 60 to 70 per cent of the questions ask you to apply a method, often a sizing or selection method that comes from the code, and only 15 to 25 per cent can be answered by recall alone. Second, the scope: sewers and private sewage systems, DWV, water service, distribution and wells, fixtures and water treatment, hydronic heating and cooling, and process and specialized piping, at the level of a journeyperson anywhere in Canada. Third, the pace and the margin: about 1 minute 55 seconds a question, and 37 wrong answers is the most you can afford.

The published weights show where the risk sits. Interior DWV alone is 20 questions, and in blocks C and D five of the six tasks open with a sizing sub-task (sewers, interior DWV, water service, distribution and private water systems), so a weak spot in hydraulic load, fixture units or grade costs marks across the paper. Cross connection control is a sub-task of the 12-question distribution task, and the official critical thinking example is about a backflow preventer. Block F is 16 questions of hydronics, more than all of Block A, which matters if your work is mostly residential service or new-home rough-in. And Block G packs medical gas, fuel gas, compressed air and more into 9 questions.

The Red Seal Program publishes no pass rate, for this trade or any other, and it does not rank the trades by difficulty, so there is no official answer to which Red Seal exam is hardest. What differs from trade to trade is published: the question count and the mix. The provincial figures we found, each counted a different way, are set out in how hard is the Red Seal exam.

10How much does a Red Seal plumber make?

For Ontario, Skilled Trades Ontario's 2025 trade report for Plumber (306A) gives an annual range of $73,000 to $107,000 and an hourly range of $37 to $55, from Workforce Planning Ontario's Labour Market Insights Report 2025. The report notes that its figures apply to the National Occupational Classification code 72300 and that other trades or occupations may be included, so they describe the plumber occupation in Ontario, not Red Seal holders alone. Pay elsewhere in Canada is not covered by that report; the Red Seal trade page points to Job Bank's Explore Careers for wages by region.

11How should you prepare?

Follow the weights. In order: C (32), D (24), E (17), F (16), A (14), B (13) and G (9). Blocks C and D together are 56 of 125 questions, 44.8 per cent; add E and it is 73, or 58.4 per cent. The four largest tasks, interior DWV (20), potable water distribution (12), fixtures and appliances (11) and hydronic piping and components (9), hold 52 of the 125 questions, 41.6 per cent.

You need 88 correct answers. A perfect score on C and D still leaves you 32 short, and a more realistic 42 of those 56 means you need 46 of the other 69. Give C and D close to half your time, interior DWV first, then E and F before A, B and G.

Rate yourself on each of the 18 tested tasks with the three levels in the Red Seal Self-Assessment Guide for Plumber (low, medium, high) and write down how many questions you expect to get right; a low rating on a large task is your first priority. Work the formula sheet until choosing the right formula is automatic, and size a building drain and its vents, a water service and a distribution system from start to finish. There is no penalty for a wrong answer, so answer everything. For a full method, see how to study for the Red Seal exam.

Official links: the Plumber Red Seal Occupational Standard page, the 2023 standard as a PDF, the exam information page (the breakdown, the question mix with the three examples, the formula sheet and the acronym list) and the Self-Assessment Guide.

12Questions people ask

How many questions are on the Red Seal plumbing exam?

The Plumber Red Seal exam (306A in Ontario) has 125 multiple-choice questions and a four-hour writing time, about 1 minute 55 seconds per question. Each question has four options and one correct answer, and the pass mark is 70 per cent, which means 88 correct answers. You can miss 37 and still pass. The questions come from seven blocks, and the largest, sewers, sewage treatment and DWV systems, has 32.

Is the Red Seal plumbing exam hard?

It is demanding mainly because it is procedural and broad. Between 60 and 70 per cent of the 125 questions test procedures and application, often sizing and selection methods from the plumbing code, and the exam covers sewers, DWV, water supply, fixtures, water treatment, hydronics and specialized systems. You need 88 correct (70 per cent). The Red Seal Program publishes no pass rate for the trade and does not rank trades by difficulty.

What are the questions on the Red Seal plumbing exam?

All 125 are multiple choice with four options. By the Red Seal Program's breakdown, 32 cover sewers, sewage treatment and DWV (20 on interior DWV alone), 24 water service and distribution, 17 fixtures, appliances and water treatment, 16 hydronic systems, 14 common occupational skills, 13 preparing and joining pipe, and 9 specialized systems such as process piping, fuel gas and medical gas. The mix is 15 to 25 per cent recall, 60 to 70 per cent procedural and 10 to 20 per cent critical thinking.

How do you become a Red Seal plumber in Ontario?

Complete a Plumber (306A) apprenticeship, which Skilled Trades Ontario sets at 9,000 hours, approximately five years (8,280 on the job and 720 in school over three levels, Grade 10 entry), or qualify as an experienced worker through its Trade Equivalency Assessment. Then pass the 125-question Red Seal exam with 70 per cent. Skilled Trades Ontario issues the Certificate of Qualification, which in this compulsory trade must be renewed to stay valid.

What does Red Seal plumber mean?

It means a plumber whose provincial or territorial certificate of qualification carries the Red Seal endorsement, earned by passing the interprovincial Red Seal exam: 125 written questions on the whole trade, built on the 2023 Red Seal Occupational Standard. Plumber is designated Red Seal in all 13 provinces and territories. It is the journeyperson credential; it is not a gas licence, which in Ontario is a separate G3 or G2 certificate.

How much does a Red Seal plumber make?

In Ontario, Skilled Trades Ontario's 2025 trade report for Plumber (306A) gives an annual range of $73,000 to $107,000 and an hourly range of $37 to $55, citing Workforce Planning Ontario's Labour Market Insights Report 2025. Those figures cover the plumber occupation code (NOC 72300) in Ontario, which may include other workers, not only Red Seal holders. Pay elsewhere in Canada is not covered by that report.

13Sources

• Red Seal Program: Plumber exam information: 125 questions, the question count for each major work activity and task, the question mix with one example of each question type, and the formula sheet and acronym list provided with the exam.
• Red Seal Program: Plumber trade page: the Red Seal trade name, the provinces and territories that use it, Quebec's title (Pipe Fitter (Plumber)), the NOC code and the standard used as the basis of the exams.
• Red Seal Occupational Standard: Plumber (2023, PDF): the 7 major work activities, 21 tasks and 95 sub-tasks, the task descriptors and range of variables, the common core markings, the note on gas licensing and the overlaps with other trades.
• Red Seal Program: Plumber formula sheet (PDF): the constants, coefficients, conversion factors and formulas provided with the exam.
• Red Seal Program: Plumber acronyms (PDF): the acronym list provided with the exam.
• Red Seal Exam Self-Assessment Guide: Plumber (PDF): the question count per major work activity and task, the rounded percentages, and the three-level self-rating used in the preparation section.
• Red Seal Exam Preparation Guide: exam format, pass mark, writing time, question types and study methods, the national code book advice, exam supplies, exam room rules and the common core rule.
• Skilled Trades Ontario: Plumber: the Ontario trade name and code (Plumber, 306A), its compulsory status and renewal rule, the apprenticeship hours and in-school topics, and the 2025 trade report linked from the page (entry level, certificates issued, pay ranges).
• Skilled Trades Ontario: Plumber curriculum standard, Levels 1 to 3 (2018, PDF): the Ontario Building Code Part 7, National Plumbing Code and natural gas piping modules.
• Skilled Trades Ontario: Trade Equivalency Assessment: the Ontario route for experienced workers who did not complete an Ontario apprenticeship.

The question counts were checked against the Red Seal Program's exam information page and Self-Assessment Guide for Plumber on September 30, 2026, and the task lists and range of variables come from the 2023 Red Seal Occupational Standard, whose task numbering both documents use. The Ontario rules, hours, certificate count and pay ranges come from Skilled Trades Ontario's Plumber trade page and its 2025 trade report, and the code topics from its 2018 Plumber curriculum standard. If the Red Seal Program changes the breakdown, its page is the final word. If you find one of ours out of date, tell us.

Related: 306A Plumber practice exam · Free 306A practice questions · How hard is the Red Seal exam · How many questions are on the Red Seal exam · Red Seal exam pass mark · Red Seal exam fees by province · How to challenge the Red Seal exam · 307A Steamfitter exam guide · All guides

14Practice for this exam

TicketPrep 306A practice tests are weighted to the breakdown above, block by block, and every answer is explained, all four options. You can try five sample questions with no account.

Ten free questions per trade, no account: free practice questions. How our questions are written and checked: how our questions are made.