Plumber · Red Seal 306A

Five 306A practice exam questions, answers included.

Q: How many questions are on the 306A Red Seal Plumber exam?

The Red Seal Plumber exam — Ontario trade code 306A — has 125 multiple-choice questions, a 4-hour writing time and a 70% pass mark, which is 88 correct answers, or about 1 minute 55 seconds per question. The questions are distributed across 7 major work activities. Between 60 and 70 percent are procedural and application questions; 15 to 25 percent are knowledge and recall, and 10 to 20 percent are critical thinking.

Q: Is the 306A practice exam free?

Yes. You can try five free Plumber practice questions with no account. You see right or wrong as you go, and your email unlocks the written explanation for every option plus a one-page study guide. A full bank of 550 questions — 400 Standard plus 150 Advanced — with mock exams is available with Exam Pass, a one-time $69 purchase for 120 days of access.

Q: What does the 306A Plumber exam cover?

The 306A exam covers common occupational skills such as safety, lock-out and tag-out, rigging, soldering and brazing, organizing the work, piping layout, supports and sleeves, trench excavation and fire stopping (14 questions); preparing and joining tube, tubing and pipe in copper, plastic, steel, cast iron and specialized materials (13); sewers, sewage treatment systems and interior drainage, waste and vent (DWV) systems (32, with 20 on interior DWV alone); water service, potable water distribution, cross connection control and private water pressure systems (24); plumbing fixtures, appliances and water treatment (17); hydronic heating and cooling piping and equipment (16); and specialized systems such as process piping, compressed air, fuel gas and medical gas (9) — the 7 major work activities of the Red Seal occupational standard. Communication and mentoring, low-pressure steam and potable water fire protection are in the standard but carry no exam questions.

Five questions from five different work activities — recall, procedural and critical-thinking, the way the exam is built. Pick an answer, then open the explanation. Every question in the bank explains all four options, not just the right one.

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A journeyperson plumber in safety glasses and a hi-vis vest at a basement rough-in, a copper manifold with red and blue PEX runs behind her and a cast-iron stack beside her — Field study306A Plumber

Critical thinking · Installs, tests and services water service and distribution

A farmhouse on well water has a rotten-egg smell from the hot taps only; the cold water smells normal, and the smell is worst after the family returns from a week away. What is the most likely cause?
1. Hydrogen sulphide gas coming from the well itself
2. Bacteria reacting with the heater's magnesium anode rod
3. Sewer gas from a dry trap near the water heater
4. A natural gas leak at the heater's gas valve
Show the answer
B. Correct. Sulfate-reducing bacteria in the warm, standing tank water turn sulfate into hydrogen sulphide, helped along by the magnesium anode; a week of no use lets it build up. Replace the anode with an aluminum-zinc or powered anode as the heater maker allows, and disinfect the heater.
Procedural · Installs, tests and services sewers, sewage treatment systems and drainage, waste and vent (DWV) systems

An apprentice vented a 1½-inch (38 mm) laundry-tub trap arm with the vent tee 40 mm downstream of the trap weir. What is wrong, and what is the fix?
1. The vent must be at least 1.8 m (6 ft) from the weir
2. Nothing; a vent as close to the weir as possible works best
3. The vent should come off the top of the trap bend itself
4. It is a crown vent; move the tee two pipe diameters or more from the weir
Show the answer
D. Correct. A vent within two pipe diameters of the trap weir is a crown vent. Waste surging over the weir is thrown into the vent opening and fouls it. The code prohibits it; move the vent downstream while staying within the maximum trap-arm length.
Procedural · Prepares and assembles tube, tubing and pipe

You are making a 3/4-inch (19 mm) PEX-A joint with a cold-expansion fitting (ASTM F1960) in a condo suite. The tube is cut square. What is the correct method?
1. Warm the tube end with a torch so it expands further
2. Expand the tube, then slide the ring over the expanded end
3. Slip the ring on, expand tube and ring together, insert the fitting
4. Push the fitting in and crimp a copper ring over the joint
Show the answer
C. Correct. The ring goes onto the tube first, then tube and ring are expanded together in steps, turning the tool between strokes. Push the fitting in at once; the tube's memory shrinks it back over the fitting ribs. Cold slows the shrink-back, so allow the maker's time before testing.
Procedural · Installs, tests and services fixtures, appliances and water treatment systems

A floor-mounted WC in a condo rocks slightly, and there is a faint sewer odour and staining on the floor at its base. The closet bolts are tight. What is the correct repair?
1. Pull the WC, repair the flange, reset on a new seal
2. Tighten the closet bolts another half-turn
3. Caulk the base all round to stop the rocking
4. Shim under the front edge and leave the seal
Show the answer
A. Correct. Rocking has already broken the wax seal, and the odour and staining show it is leaking. Isolate and drain the WC, lift it, inspect the flange (broken ring, loose screws, set below the finished floor) and repair it with a repair ring or spacer, then reset level on shims with a new wax ring or waxless seal and recheck for rocking.
Recall · Installs, tests and services low-pressure steam and hydronic systems

In a closed hydronic system, what is the point of no pressure change?
1. The highest point, where the air vents sit
2. The lowest point, where static pressure is highest
3. Wherever the expansion tank connects to the piping
4. The circulator discharge, where pump head peaks
Show the answer
C. Correct. The tank's cushion sets the pressure where it connects, and that pressure stays the same whether the circulator runs or not. With the circulator's suction there (pumping away from the tank), the pump's head appears as a pressure rise through the system, keeping air in solution and vents working.

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The 306A exam at a glance

What you're walking into.

Questions: 125
Time limit: 4 hrs
Work activities: 7
Our bank: 550

Question mix — weighted to the blueprint

Recall 15–25%Procedural 60–70%Critical 10–20%

The 306A is a procedural exam: 60 to 70 percent of the paper asks you to carry out a method, 15 to 25 percent asks you to recall a fact, and 10 to 20 percent hands you a situation to diagnose. The method is usually a plumbing one — sizing a drain and its vents from the hydraulic load, setting grade, choosing the cross connection control that suits the hazard, testing a DWV system, setting up a well pump and pressure tank — and the wrong answers are the steps people get out of order or the device that almost fits. Sewers, sewage treatment and DWV (32 questions) is the heaviest block, and water service and distribution (24) comes next — 56 of the 125 questions between them. One task, interior DWV, carries 20 questions on its own.

The pass mark is 70 percent, which is 88 correct answers out of 125, and four hours works out to about 1 minute 55 seconds a question. A formula sheet and an acronym list are provided at the sitting. The exam is built on the 2023 Red Seal Occupational Standard for Plumber. In Ontario, Plumber (306A) is a compulsory trade with a 9,000-hour apprenticeship; the other provinces and territories call the trade Plumber too, Quebec calls it Pipe Fitter (Plumber), and it is the same exam.

The full Plumber Red Seal practice exam

Know your real 306A score before exam day.

Free, Red Seal–style practice for the 306A Plumber certification. Every test is weighted to the official exam blueprint — about two thirds procedure, the rest recall and critical thinking, the way the real exam is built — so the score you get here reflects the score you'd get there.

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What the 306A covers

Seven major work activities.

The occupational standard groups the trade into 7 major work activities, 21 tasks and 95 sub-tasks, 85 of them common core. The question counts below are the official blueprint weightings — our 550-question bank is built to that same map, with every common-core sub-task covered. Drainage leads: sewers, sewage treatment and DWV carries 32 of the 125 questions, 20 of them on interior DWV alone. Water service and distribution (24) follows, then fixtures, appliances and water treatment (17), hydronic systems (16), common occupational skills (14), tube, tubing and pipe (13) and specialized systems (9).

A
Performs common occupational skills · 14 questions
Safety-related functions — the work environment, PPE and lock-out and tag-out (3 questions); using and maintaining tools and equipment, including access equipment, rigging and crane loads, welding, and soldering and brazing (3); organizing the work — project tasks, materials and documentation (3); and routine trade activities (5): piping layout and length calculations, supports and sleeves, commissioning, protecting piping, trench excavation and fire stopping. Communication and mentoring are in the standard but carry no questions.
B
Prepares and assembles tube, tubing and pipe · 13 questions
Preparing tube, tubing and pipe (6 questions) — inspecting, cutting, bending and preparing connections by reaming, threading and grooving — and joining it (7), with one sub-task per material: copper, plastic, steel, cast iron, and specialized pipe such as glass.
C
Installs, tests and services sewers, sewage treatment systems and drainage, waste and vent (DWV) systems · 32 questions
Sanitary, storm and combined sewers (7 questions): sizing from hydraulic load and grade, maintenance holes and catch basins, and hydrostatic, smoke, air and mandrel tests; sewage treatment systems (5), from septic and holding tanks and leaching beds to lagoons and treatment plants; and interior DWV (20), the largest single task on the exam — sizing the sanitary drainage and its vent piping from the building's hydraulic load and the storm drainage from the roofs and paved areas it serves, then the hydrostatic, pneumatic and final smoke or 25 mm water-column tests. The heaviest block on the paper.
D
Installs, tests and services water service and distribution · 24 questions
Water service (6 questions), sized from fixture units, developed length, elevation, pressure and velocity and held with thrust blocks, mechanical restraints and tie rods; potable water distribution (12) — friction loss, pressure-reducing valves, water heaters, tempering valves and shock arrestors, and cross connection control from air gaps to reduced pressure backflow preventers; and private water pressure systems (6): wells, cisterns and surface sources, jet, submersible and booster pumps, and pressure tanks.
E
Installs, tests and services fixtures, appliances and water treatment systems · 17 questions
Plumbing fixtures and appliances (11 questions) — supports and carriers, the fixtures themselves, appliances such as water heaters and dishwashers, and water-saving trim, then testing and servicing them — and water treatment systems (6), sized from a water test for hardness, pH and total dissolved solids: filtering, softening, UV, reverse osmosis and neutralizing.
F
Installs, tests and services low-pressure steam and hydronic systems · 16 questions
All 16 questions are hydronic: low-pressure steam is in the standard but is not common core, so it carries none. Hydronic piping and components (9 questions) — one-pipe to four-pipe and primary/secondary designs, air removal, expansion tanks, circulators, terminal units, controls and glycol — and hydronic heating and cooling equipment (7): 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.
G
Installs, tests and services specialized systems · 9 questions
Process piping (5 questions) for food processing, high-purity water, treatment plants and laboratories, and other specialized systems (4): compressed air, natural gas and propane piping, medical gas and vacuum, radon mitigation, irrigation, ground-source loops, solar thermal and rainwater harvesting. Potable water fire protection is in the standard but is not common core, so it carries no questions.

Where our numbers come from

Every question, anchored to the standard.

Plumbing practice banks quietly go wrong in two ways: a figure from the wrong code — often a US model code, sometimes one province's amendment — presented as the Canadian rule, and formulas tested as memory when the exam hands you a formula sheet. Every question in our 306A bank is anchored to a sub-task of the occupational standard and verified against it, with all four options explained. Code questions follow the National Plumbing Code of Canada, the national code book the Red Seal exam refers to, and where a value is set by the code table, the authority having jurisdiction, the manufacturer or the spec — a fixture-unit load, a trap-arm length, a test pressure, a tank precharge — the question gives it in the stem instead of inventing a single right answer. The formula sheet and acronym list are provided at the exam sitting — constants such as 0.433 psi per foot of head and 1.414 for a 45° offset, expansion coefficients, Boyle's and Charles' laws, grade, softener grains and the hydronic Btuh = gpm × 500 × ΔT — so our calculation questions are worked from that sheet, with pipe sizes in the trade's nominal inches and the metric size alongside, and we never test recall of the formulas themselves. Communication and mentoring, low-pressure steam and potable water fire protection carry no exam questions, so the bank does not test them. The question counts above are the Red Seal Program's own exam breakdown for Plumber, and every question is mapped to a sub-task of the Red Seal Occupational Standard. The current exam and this bank follow the 2023 standard. For what each block covers and where to spend your study time, read the 306A Plumber exam guide. Read how our questions are made.

Last reviewed September 30, 2026 against the Red Seal Program's published exam information.

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Why practice scores mislead

You can ace recall and still fail the 306A.

Only 15 to 25 percent of the 306A asks you to state a fact — a fitting, a device, a term from the acronym list. That is exactly why recall drills leave plumbers over-confident. Between 60 and 70 percent of the paper is procedural, and it tests the order and the method behind the fact. Knowing what a crown vent is does not tell you where the vent tee has to go on a laundry-tub trap arm. Knowing what a backwater valve does does not tell you what its annual service includes. Knowing that PEX-A expands does not tell you whether the ring goes on before or after the tube is expanded. And the sizing questions — a building drain and its vents from the hydraulic load, a water service from fixture units, a well pump from total dynamic head — ask you to work a method, not name a part. Then 10 to 20 percent is critical thinking — a pressure gauge that creeps up to street pressure overnight, a relief valve that drips as the boiler reaches temperature, hot water that smells of rotten eggs — where you have to read the evidence and name the cause. The formula sheet gives you the constants and the formulas but no fixture-unit or pipe-sizing tables, so the method behind them is yours to bring. That gap is why people walk in confident and walk out surprised. TicketPrep weights every test to the published blueprint, so a 78 here means 78 there — and a weak block here is a weak block there.

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How TicketPrep prepares you

Built like a study tool, not a quiz app.

Weighted to the blueprint

Every test matches the published 306A weightings — recall, procedure and critical thinking in the same proportions the real exam is built from.

Every answer explained

Learn why the right answer is right — and why each of the other three is wrong. That's where the learning happens.

Timed mock exams

Full-length tests that match the real 125-question count and 4-hour limit, so exam day feels familiar.

Know your weak areas

Your score broken out by work activity, so you always know which block to drill next.

306A questions

Before you start.

How many questions are on the 306A Red Seal Plumber exam?

125 multiple-choice questions with a 4-hour writing time and a 70% pass mark — 88 correct answers — distributed across 7 major work activities. That is about 1 minute 55 seconds per question. Between 60 and 70 percent are procedural and application questions; 15 to 25 percent are knowledge and recall, and 10 to 20 percent are critical thinking.

Is 306A the same as the Plumber Red Seal exam?

Yes. The Red Seal trade is called Plumber. Ontario certifies it as Plumber, trade code 306A, and issues the Certificate of Qualification through Skilled Trades Ontario when you pass the same interprovincial exam. Twelve provinces and territories use the title Plumber; Quebec calls the trade Pipe Fitter (Plumber). Whichever province you write in, it is one exam, built on the 2023 Red Seal Occupational Standard.

Is the 306A practice exam free?

Yes. You can try five free sample questions with no account. You see right or wrong as you go, and your email unlocks the written explanation for every option plus a one-page study guide. The full 550-question bank — 400 Standard plus 150 Advanced — and mock exams come with Exam Pass — a one-time $69 purchase for 120 days of access, not a subscription.

What does the 306A Plumber exam cover?

Common occupational skills (safety, lock-out and tag-out, rigging, soldering and brazing, organizing the work, piping layout, supports and sleeves, trench excavation and fire stopping, 14 questions); preparing and joining tube, tubing and pipe in copper, plastic, steel, cast iron and specialized materials (13); sewers, sewage treatment systems and interior drainage, waste and vent (DWV) systems (32, with 20 on interior DWV alone); water service, potable water distribution, cross connection control and private water pressure systems (24); plumbing fixtures, appliances and water treatment (17); hydronic heating and cooling piping and equipment (16); and specialized systems such as process piping, compressed air, fuel gas and medical gas (9) — 7 major work activities in all. Communication and mentoring, low-pressure steam and potable water fire protection are in the standard but carry no exam questions.

Is there a formula sheet on the Plumber exam?

Yes. The Red Seal Program provides a formula sheet and an acronym list at the exam 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, force, gpm, grade, softener grains, storm water, Watt's law and pressure, the hydronic Btuh = gpm × 500 × ΔT, and areas and volumes. The acronym list covers terms such as DWV, NPC, RP, DCVA, PRV, T&P and LWCO; it gives you the meaning, not what the thing does. The sheet has no fixture unit, hydraulic load or pipe sizing tables. Our calculation questions are written to be worked from the sheet, with any table value you need given in the question, so you practise choosing and applying the right formula the way the exam presents it.

Is plumber a compulsory trade in Ontario?

Yes. Plumber (306A) is a compulsory trade in Ontario: to work in it you must hold a Registered Training Agreement, a Provisional Certificate of Qualification or a Certificate of Qualification and appear on Skilled Trades Ontario's Public Register, and the Certificate of Qualification must be renewed to stay valid. The apprenticeship is 9,000 hours, approximately five years — 8,280 on the job and 720 in school over three levels.

Does the Red Seal plumbing exam include a gas licence?

No. The Red Seal Plumber exam is a written exam on the plumbing trade, and passing it earns the Certificate of Qualification with the Red Seal endorsement, not a gas ticket. The standard says plumbers install gas piping from the point of supply to the appliance isolation valve where provincial rules allow, but in Ontario the G3 and G2 gas technician certificates are issued separately by the Technical Standards and Safety Authority (TSSA), with their own exams.

Are these real 306A exam questions?

No. These are independent, Red Seal–style practice questions written for study, each mapped to the public occupational standard for the trade. Anyone selling "real exam questions" is breaking the Red Seal Program's terms — we don't do that.

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