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Ontario · Certificate of Qualification
Ontario 306A Plumber exam guide
Understand the two eligibility routes, the Red Seal exam format and a practical way to organize your preparation before booking the certifying exam.
- Ontario trade code
- 306A
- Apprenticeship
- 9,000 hours
- Red Seal exam
- 125 questions
- Pass mark
- 70%
What 306A means
Plumber is a compulsory Red Seal trade in Ontario.
Ontario uses the trade code 306A for Plumber. Skilled Trades Ontario describes the work as installing, repairing and maintaining piping systems, fixtures and plumbing equipment used for water distribution, drainage and waste disposal.
Because Plumber is a compulsory trade, a person practising it legally in Ontario must hold an accepted status and appear on the Skilled Trades Ontario Public Register. Passing the certifying exam leads to an Ontario Certificate of Qualification; the trade also participates in the Interprovincial Red Seal Program.
Eligibility
There are two main routes to exam eligibility.
Preparation software cannot approve a candidate. Confirm your status with Skilled Trades Ontario before paying for a course or booking travel.
01
Complete an Ontario apprenticeship. The current program totals 9,000 hours: 8,280 hours of on-the-job experience and 720 hours of in-school training across three levels.
02
Apply as an experienced worker. A Trade Equivalency Assessment is available to people who did not complete an Ontario apprenticeship but can document equivalent skills and experience.
03
Receive authorization. Eligible candidates follow the instructions in their Authorization to Test Letter and use the official scheduling process.
04
Check current fees and accommodations. Amounts and procedures can change, so use the current exam-scheduling page rather than an undated third-party summary.
Exam structure
Prepare for application, not only recall.
The Red Seal Plumber exam has 125 multiple-choice questions, four choices per question, a four-hour writing time and a 70% pass mark. The official blueprint currently allocates the largest question group to sewers, sewage treatment systems and drainage, waste and venting systems.
Procedural and application
Choosing the correct material, sequence, installation method or response in a trade situation.
Critical thinking
Interpreting information, diagnosing a condition and selecting the best conclusion.
Study plan
Use the blueprint to decide what to practise next.
1
Start with a mixed diagnostic so weak work areas are visible instead of guessed.
2
Practise one work area at a time, especially code navigation, calculations and procedures you answer slowly.
3
Review incorrect answers and explain the rule or reasoning in your own words before retrying.
4
Use timed mixed sets near the exam date, but keep checking the official blueprint and current exam instructions.
Primary sources
Check the authority, not just a study summary.
This page was reviewed against the official sources below on August 19, 2026. Rules, fees and scheduling procedures can change.
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