Plumbing is a compulsory trade in Ontario. To do plumbing work you must be a registered apprentice or hold a Certificate of Qualification (or a provisional one). This guide explains the Ontario Plumber (306A) apprenticeship from first application to Red Seal.
What plumbers do
Plumbers install, test and repair drain, waste and vent (DWV) systems, water supply and distribution, fixtures and appliances, and in many jobs hydronic heating and low-pressure steam. The work spans new residential and commercial construction, service and renovation, and institutional maintenance. See our Plumber trade guide for the full scope.
Step 1: Entry requirements
Skilled Trades Ontario lists Grade 10 as the minimum academic standard. Grade 12 math is a real advantage for pipe offsets, grade and fixture-unit calculations. High-school students can get a head start through OYAP.
Step 2: Find a sponsor
Plumbing contractors, service companies and UA locals all take apprentices. Many apprentices start as plumber's helpers or labourers. Check current plumber jobs from Job Bank, and read our guide to getting your first apprentice job.
Step 3: Register
You and your sponsor sign a Registered Training Agreement with the Ministry. Because plumbing is compulsory, you need this before you start doing plumbing work. Keep copies of your agreement, pay stubs and logbook. Our apprenticeship guide explains the process and supports such as EI during school and the Canada Apprentice Loan.
Step 4: Three levels of in-school training
The 306A program has three levels of in-school training totalling 720 hours on STO's chart. Topics include the Ontario Building Code (plumbing parts), drawings, piping materials and joining methods, DWV and water systems, fixtures, and hydronics. Training is offered at colleges and union training centres across Ontario.
Step 5: The certifying exam
Once you complete your hours and school, you write the Red Seal Plumber exam: 125 multiple-choice questions with a 70% pass mark. The biggest block is sewers, sewage treatment and DWV systems (32 questions), followed by water service and distribution (24) (Red Seal exam information). Book through Skilled Trades Ontario. Prepare with our Red Seal exam guide, our study tips and the free plumber practice sample.
As a compulsory trade, your Certificate of Qualification must be renewed every year (Skilled Trades Ontario).
Related trades
If industrial piping interests you more than buildings, look at Steamfitter/Pipefitter, another compulsory Ontario trade. Gas work in Ontario also requires a separate gas technician certificate from the TSSA.
What plumbers earn
Job Bank's 2025 data for NOC 72300 (Plumbers) shows a median of $32.50/hour in Ontario, with the high end at $50.38/hour (Job Bank wages, 2025). Apprentices start at a percentage of the journeyperson rate.
Checklist
- Meet the Grade 10 minimum (Grade 12 math recommended)
- Find a sponsor and sign a Registered Training Agreement before doing plumbing work
- Complete 3 school levels and 9,000 total hours
- Pass the 125-question Red Seal exam
- Renew your C of Q every year
What first-year apprentices actually do
Early on, expect to carry material, cut and prep pipe, dig and support trenches, and help a journeyperson rough in DWV and water lines. On service jobs you'll learn to diagnose leaks, clear drains and replace fixtures and water heaters. As you progress, you'll lay out systems from drawings, size piping and run pressure tests. Your logbook lists the skills your trainer has to sign off, so ask to rotate through different kinds of work.
Tips for getting sponsored
- Have your own basic hand tools, CSA-approved boots and reliable transportation.
- Get Working at Heights training if you're aiming for construction. It's required for many Ontario construction jobs.
- Call or visit local plumbing and mechanical contractors. Service companies often hire helpers year-round.
- Check UA local apprenticeship intakes and application windows.
- Be honest about what you know. Sponsors care more about reliability and a willingness to learn than prior experience.
Frequently asked questions
How long is a plumbing apprenticeship in Ontario?
The 306A program is 9,000 hours in total: 8,280 hours on the job and 720 in school over three levels. Working full time, most apprentices take about five years.
Can I do plumbing work without being an apprentice?
No. Plumbing is compulsory in Ontario. Under the Building Opportunities in the Skilled Trades Act, 2021, you must be working under a registered training agreement, or hold a Certificate of Qualification or a provisional one, unless a regulation exempts you.
Is plumbing hard on the body?
It can be. Expect kneeling, lifting, work in tight spaces and some exposure to weather on new construction. Good knee pads, lifting technique and PPE make a real difference over a career.
Can I become a gas fitter too?
Yes, many plumbers also earn a TSSA gas technician certificate, which opens up appliance and heating work. It's a separate certification with its own training and exams.
What if I trained as a plumber in another province or country?
If you hold a Red Seal endorsement, Ontario generally recognizes it. Without one, Skilled Trades Ontario's Trade Equivalency Assessment is the usual route to qualifying for the exam.
This article is general information for people exploring trades careers in Canada. Rules, programs and amounts change and differ between provinces and territories — confirm details with your apprenticeship authority and official government sources.