Using the RSOS and exam weightings

On the second Saturday of her study plan, Luis asked Maya a question she could not answer. "If you had sixty hours to study, how many would you give to venting?" She guessed ten. He opened the Red Seal exam weightings for plumbers on his laptop and showed her that sanitary drainage, sewers and venting together carry about a quarter of the exam, while specialized systems such as medical gas and fire protection carry under a tenth. "The people who wrote this exam told you where the marks are," he said. "Most apprentices never look."

This lesson shows how to read the Red Seal Occupational Standard, how the exam weightings follow from it, and how to turn the weightings and an honest self-assessment into a study plan with hours attached. The same method works for any exam that publishes a blueprint.

What the Red Seal Occupational Standard is

The Red Seal Occupational Standard, usually shortened to RSOS, is a national description of the plumber trade, developed by the provinces and territories with industry and reviewed on a regular cycle. It breaks the trade into major work activities, each major work activity into tasks, and each task into sub-tasks. For each sub-task it lists performance criteria, which describe what a competent plumber does, and knowledge criteria, which describe what they need to know. The exam questions are written against these sub-tasks, so the RSOS is the closest thing a candidate has to a list of every topic the exam can ask about.

The RSOS is long, and Maya did not try to read it cover to cover. She used it as a checklist. For each task, she read the sub-task titles and asked herself whether she could explain the work to an apprentice and answer a question about it. Where the answer was no, she marked it for study. The knowledge criteria were especially useful, because they named things she had done on the job without learning the theory, such as the principles of steam traps and the chemistry behind water treatment.

The weightings by major work activity

The Red Seal exam weightings show how many questions come from each major work activity. For the plumber exam, the seven major work activities and their approximate shares are listed below, with the number of questions each share represents on a 125-question exam.

Two things stand out. First, the two largest major work activities, C and D, are the drainage and water supply systems that plumbers spend most of their time on, and together they are 45 per cent of the exam. Second, the hydronic heating share, 13 per cent, is as large as the fixtures share and larger than the share for pipe preparation. Many apprentices in Ontario spend little time on hydronic systems at work, so this is where unprepared candidates lose marks. Luis called it the quiet sixteen questions.

Turning weightings into study hours

A study plan that follows only the blueprint gives the most time to the biggest areas, even if the candidate already knows them well. A plan that follows only weaknesses spends hours on small areas. The useful plan combines both. Maya rated herself from 1 to 5 in each area, where 1 meant she would struggle with most questions and 5 meant she would get almost all of them right. Each area's priority was its share of the exam multiplied by a weakness factor, and her available hours were divided in proportion to the priorities.

The factor of 6 minus the rating is a simple choice, and it works because it never reaches zero: even an area rated 5 gets some review time. Some candidates square the factor to push more time toward weak areas. The exact formula matters less than doing the calculation at all, because it turns a vague feeling about what to study into a schedule.

# Weighted study plan: exam share x weakness factor
hours = 60
areas = {   # area: (share of exam, self-rating 1 to 5)
    "A Common occupational skills": (0.11, 3),
    "B Tube, tubing and pipe":      (0.10, 4),
    "C Sewers and DWV":             (0.26, 4),
    "D Water service/distribution": (0.19, 3),
    "E Fixtures, appliances, treatment": (0.13, 4),
    "F Low-pressure steam/hydronic": (0.13, 2),
    "G Specialized systems":        (0.08, 2),
}
prio = {a: share * (6 - rating) for a, (share, rating) in areas.items()}
total = sum(prio.values())
print(f"Total priority {total:.2f}")
print(f"{'Area':36s} share rating  hours")
for a, p in sorted(prio.items(), key=lambda kv: -kv[1]):
    share, rating = areas[a]
    print(f"{a:36s} {share * 100:4.0f} %   {rating}    {hours * p / total:5.1f}")
print(f"{'Total':36s}              {hours:5.1f}")

Total priority 2.72
Area                                 share rating  hours
D Water service/distribution           19 %   3     12.6
C Sewers and DWV                       26 %   4     11.5
F Low-pressure steam/hydronic          13 %   2     11.5
A Common occupational skills           11 %   3      7.3
G Specialized systems                   8 %   2      7.1
E Fixtures, appliances, treatment      13 %   4      5.7
B Tube, tubing and pipe                10 %   4      4.4
Total                                              60.0

Run the program with your own ratings. Rate yourself after a diagnostic test rather than from memory, because people tend to overrate areas they enjoy and underrate areas they have not looked at in a while. Maya re-rated herself after each mock exam and reran the plan, which moved hours from areas she had fixed to areas that were still weak.

Reading a task in the RSOS

To see how the RSOS turns into questions, Luis walked Maya through one task in major work activity C: installing venting systems. The sub-tasks include determining the type and size of vents required, installing vent piping, and testing the venting system. The knowledge criteria list the purpose of venting, the types of vents, the effect of trap seal loss, and the code requirements for vent sizing, grade and connections. Every one of those lines can become a question.

Writing questions from the blueprint like this is the method Maya's study group used. It forces a close reading, and it produces practice questions aimed exactly at the exam's topics. The questions in this course were written the same way.

The code you will be tested on

The Red Seal exam is national, so its code questions follow the National Plumbing Code of Canada. Ontario's plumbing rules, in Part 7 of the Ontario Building Code, are closely based on the national code and organized the same way: general requirements, materials and equipment, piping, drainage systems, venting systems, potable water systems and non-potable water systems. Where Ontario differs from the national code, the exam follows the national rules, but the exam rarely turns on a provincial difference. Luis's advice was to study the principles and the national values, and to be aware of where Ontario's rules differ so that a familiar number from work does not mislead you.

Because the exam provides the code information a question needs, candidates do not have to memorize table values. They do need to know how a table is used: which column to read, how to add loads, what a footnote changes and when an exception applies. A candidate who knows how the drainage tables work can answer a question that quotes an extract of one in under two minutes. A candidate who has never used them cannot.

• Ontario-specific items to watch: the rules for hot water temperature at showers and bathtubs, backflow and cross-connection programs run by municipalities, and the treatment of sumps and backwater valves in local by-laws. The exam tests the principle; your job will test the local rule.
• Definitions are worth studying for both. Many questions turn on a definition: what counts as a branch, a stack, a fixture drain, a developed length or a building drain. Definitions in the code are precise, and the exam uses them precisely.

A diagnostic test before the plan

Before writing her study plan, Maya took a diagnostic test: fifty mixed practice questions in about an hour and a half, without preparation, timed. The point was not the score but the pattern. She sorted her wrong answers by major work activity and compared her accuracy in each with her self-ratings. Two surprises came out. She had rated herself 4 on water service and distribution, but got only 60 per cent of those questions right, mostly because of sizing problems with several steps. And she had rated herself 2 on specialized systems, but got 80 per cent, because her medical gas work on the hospital wing had taught her more than she realized.

She reran the plan with ratings based on the diagnostic. Hours moved from areas she had overrated to areas she had not. That is the value of a diagnostic: it replaces opinion with evidence, early enough to change the plan.

Keeping the plan honest

A plan on paper does not study itself. Maya put her hours into a calendar as fixed blocks: three evenings a week for ninety minutes, and four hours on Saturday mornings. Each block had a topic from the plan and a product at the end: ten questions answered, a summary page written, a set of sizing problems worked. When a block was missed, it was moved, not dropped. Luis checked her notebook every Monday at the start of the shift, which she found irritating for about two weeks and then relied on.

She also kept a running total of hours against the plan. By week six she was behind on water supply and ahead on fixtures, so she moved two Saturday blocks. That kind of adjustment is what makes a plan work. A plan that is never changed is usually a plan that is not being followed.