How to Become a Plumber Apprentice in Ontario

The path in one paragraph

A plumbing apprenticeship in Ontario is an employer-first path into the 306A trade: Plumber, the trade that lays out, assembles, installs, and repairs the piping, fixtures, and drainage systems buildings run on. Get hired by a plumbing contractor or union local willing to sponsor you, register the training agreement with Skilled Trades Ontario, then work about five years of paid on-the-job hours (8,280 of them) interleaved with three classroom levels (720 hours). Pass the certifying exam, earn the Certificate of Qualification with its Red Seal endorsement, and you hold the credential Ontario plumbing employers ask for by name.

First: compulsory means registration is not optional

Ontario classifies trades as compulsory or voluntary, and plumbing sits firmly in the first camp. Plumber (306A) is a compulsory trade: you must be a registered apprentice or hold the Certificate of Qualification to perform plumbing work in Ontario. That is the legal fact, stated on Skilled Trades Ontario's own trade page and preserved in the province's trade regulations. The practical consequence is the opposite of a voluntary trade like millwright — you cannot start earning hours informally and sort out the paperwork later. Your hours only count once a Registered Training Agreement ties you to a sponsoring employer, and working the trade outside that structure is not permitted. Treat the registration as step one, not paperwork.

Step 1: Meet the entrance requirements

The official minimum from Skilled Trades Ontario's apprenticeship chart (June 2026) is Grade 10, and you must be at least 16 years old. You also need legal permission to work in Canada with a valid social insurance number and, critically, a sponsoring employer in Ontario before you register with Skilled Trades Ontario.

Treat Grade 10 as the floor, not the target. The three classroom levels run on applied math (pipe sizing, drainage calculations, pressure and flow), trade science, and construction drawings. Employers hiring apprentices routinely list Grade 12 math and science as the real bar, and college pre-apprenticeship programs assume them. If you are still in high school, the Ontario Youth Apprenticeship Program (OYAP) lets you start banking apprenticeship hours and even in-school training before graduation.

Step 2: Find a sponsoring employer and register the agreement

This is the step that starts the clock. Your hours only count once a Registered Training Agreement ties you to a sponsoring employer:

1. Get hired where pipes get run. Residential service and repair shops, commercial and industrial mechanical contractors, new-construction plumbing crews, and institutional maintenance departments all sponsor apprentices. Real apprentice postings ask for a high school diploma, basic hand and power tool experience, and mechanical aptitude; a college pre-apprenticeship certificate or mechanical-techniques course answers the question every contractor asks: "will this kid slow my journeyperson down?" You are selling yourself as a reliable first-year with tool skills, not as a plumber.
2. Register with Skilled Trades Ontario. The application goes in once you have the sponsor; the agreement is registered and both you and your employer sign it. That document is what makes your on-the-job hours official. Do not let an employer tell you they will "sort the paperwork out later" — unregistered hours do not count.
3. Work under qualified supervision. A licensed plumber signs off each skill in your training standard as you demonstrate it. Plumbing is one of the trades subject to journeyperson-to-apprentice ratio rules, which means a sponsor needs enough licensed journeypersons on staff to supervise the apprentices it registers. If a two-person shop says it will take on three apprentices, that is a sign to verify the ratio with Skilled Trades Ontario before you sign.

The sponsor hunt is a job search in every sense: our job hunting guide walks through Job Bank, Canadian resume conventions, and the NOC codes (72300 for plumbers) you will use on applications.

Step 3: Consider the union track

Toronto's UA Local 46 — the United Association local representing more than 11,700 plumbers, steamfitters, and welders — runs its own apprenticeship program: you apply to the local, pass its aptitude testing and interview process, and get placed with a union contractor at negotiated wage rates with pension and health and welfare benefits. The training content is the same 306A program and the same exam; the difference is the employer pipeline, the wage scale, and the benefits package. Check the local's current intake schedule and application requirements before you plan around it — union intakes run on their own calendar.

Step 4: Work through the five-year program

The official numbers from the Registrar of Skilled Trades Ontario: 8,280 hours of on-the-job work experience plus 720 hours of in-school training, for 9,000 hours total over about five years. The classroom runs in three levels of 240 hours each, covering workplace safety, rigging and hoisting, pipe and fitting materials, tools and piping methods, fixtures and appliances, the properties of water and heat transfer, trade calculations, construction drawings, codes and standards, drainage and venting, sewage disposal, and water distribution systems. Delivery varies by school: most colleges run block release (several full-time weeks at a stretch) with day-release options in some locations.

Two notes that matter. First, each level ends with exams you must pass to advance; the hours alone do not promote you. Second, you are an employee the whole way through. Apprentices are paid by their employer while learning on the job, and Employment Insurance covers apprentices during full-time technical training, so apply before your school block starts since processing takes time.

Step 5: Pay for the technical training

School is the cheap part of this trade. The three 240-hour classroom levels are delivered by Training Delivery Agents — Ontario colleges and union training centres — at a few thousand dollars per level depending on the school, and you earn a wage between blocks. You will also need CSA-approved safety glasses and safety boots for day one, plus textbooks. The funding picture is straightforward:

• The Canada Apprentice Loan covers up to $4,000 per period of technical training, interest-free, with no payments due until you finish or leave the program. Available everywhere except Quebec.
• Employment Insurance covers apprentices while they attend full-time technical training. Apply before your school block starts.
• Skip the federal apprentice grants: the Apprenticeship Incentive Grant ($1,000 per level) and the Apprenticeship Completion Grant ($2,000) closed on March 31, 2025. Older guides and forums still describe them as live; they are not.

Step 6: Write the exam and hold the credential

With the hours and school levels done, you write the certifying exam administered by Skilled Trades Ontario. Scoring 70% or higher earns the Certificate of Qualification (306A), and because Plumber is an Interprovincial Red Seal trade, the exam carries the Red Seal endorsement: the national stamp that lets you work the trade anywhere in Canada without re-certifying. Ontario employers post the band openly: Job Bank's range runs $20.00 to $50.38 per hour with a $32.50 median, and late-stage apprentices are commonly at $30 or more. And if you ever want the business side, our guide to starting your own plumbing company walks through costs, licensing, and pricing — including the pro-side hourly-rate math and rough-in pricing.

Related guides

• How to start a plumbing apprenticeship in Canada — the national comparison: how Ontario's 306A regime stacks up against Alberta, BC, and the other provinces.
• How to become a plumber apprentice in BC — the west-coast path through SkilledTradesBC, for comparison.
• How to Become a Plumber Apprentice in Manitoba — the companion guide; Apprenticeship Manitoba system, voluntary Red Seal trade, four levels and 7,200 hours, RRC Polytech training
• How to Become a Plumber Apprentice in Quebec — the companion guide; CCQ certificate system, DEP first, 150-hour guarantee letter, 8,000 hours, provincial exam
• How to get your Red Seal endorsement in Canada — the certifying exam carries the Red Seal endorsement: routes, format, fees, and the national portability it buys.
• How to start job hunting in Canada — the sponsor hunt is a job search: Job Bank, Canadian resume conventions, and the NOC codes you will use on applications.
• How to start your own plumbing company in Canada — the natural next step after the ticket: startup costs, insurance, licensing, and how to price your work.
• Apprenticeship financial support in Canada — the full funding picture: Canada Apprentice Loan, EI during school, and what replaced the closed grants.

Where to train

Our trade schools directory lists approved plumbing training programs by province — Ontario, BC, Alberta — public colleges, union training centres, and pre-apprenticeship programs, every one verified against the provincial apprenticeship authority.

Sources

• Skilled Trades Ontario, Plumber trade page (compulsory status, Red Seal trade, 9,000-hour program — 8,280 on-the-job plus 720 in-school, three levels, Building Opportunities in the Skilled Trades Act, 2021 authority) —
• Skilled Trades Ontario, Apprenticeship Programs Quick Facts Chart (June 2026 — Plumber 306A — Red Seal Yes, Compulsory, certifying exam Yes, Grade 10, 3 levels, 720 in-school, 8,280 on-the-job, 9,000 total) —
• Mohawk College, Plumber apprenticeship (9,000 hours — 8,280 on-the-job plus 720 in-school at the Stoney Creek Campus for Skilled Trades; PPE requirements) —
• Job Bank, plumber wages Ontario NOC 72300 (low $20.00, median $32.50, high $50.38) via Workzen 2026 compilation
• Herzing College, plumber salaries in Ontario (late-stage apprentices at least $30 per hour; licensed plumbers typically $30–$45 per hour; postings reviewed)
• UA Local 46, Our Trades (Toronto union apprenticeship — 16-plus, learn-while-you-earn, union contract with pension and health benefits; 11,700 plumbers, steamfitters, and welders) —
• O. Reg. 175/11, s. 2(4)–(5) (Plumber listed among construction trades subject to journeyperson-to-apprentice ratios; designated a compulsory trade)

Fees, wages, and program details move — verify current figures with Skilled Trades Ontario and the training institution before you enrol.