Five free practice questions on safety, tools and common trade skills: block A of the Red Seal 306A Plumber exam, about 14 of its 125 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A 10 m (33 ft) straight horizontal run of 3-in (75 mm) ABS drain crosses a strip-mall ceiling. The code table in force gives 1.2 m (4 ft) as the maximum hanger spacing for this pipe. With a hanger at each end, what is the fewest hangers that meets the spacing?
- 11 hangers
- 9 hangers
- 10 hangers
- 8 hangers
Show the answer
C. Correct. 10 m ÷ 1.2 m = 8.3, rounded up to 9 spaces (1.11 m each); hangers = spaces + 1 = 10. Add supports wherever the code or the maker also calls for them, such as at changes of direction.
Why not the others
A. This counts 9 spaces plus 1 and then adds an end hanger again. Spaces + 1 already puts a hanger at each end, so 10 is enough.
B. Nine is the number of spaces (8.3 rounded up). Hangers at both ends of 9 spaces make 10 hangers.
D. 10 ÷ 1.2 = 8.3; rounding down to 8 spaces makes each space 1.25 m, over the 1.2 m maximum, and 8 counts spaces rather than hangers. Round the spaces up to 9, then add one: 10 hangers.
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A 1800 lb (816 kg) cast-iron boiler block is lifted with a chain block and a two-leg bridle, each leg at 45° from horizontal. Using a sling-angle factor of 1.414 for 45°, what is the tension in each leg?
- 2545 lb
- 1273 lb
- 1800 lb
- 900 lb
Show the answer
B. Correct. Load per leg = 1800 ÷ 2 = 900 lb, × the 45° factor 1.414 = 1273 lb (577 kg). Every sling leg, shackle and hook must have a WLL at least that high; flatter angles raise the tension further (factor 2.000 at 30°).
Why not the others
A. This multiplies the whole load by the factor without first dividing it between the two legs. Per-leg tension is (1800 ÷ 2) × 1.414 = 1273 lb.
C. 1800 lb is the whole load, as if one leg carried it all. With two legs the load is split, and then the angle factor is applied.
D. 900 lb is each leg's share if the legs hang vertically. At 45° each leg also pulls sideways, so its tension is higher: 900 × 1.414 = 1273 lb.
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A crew of two will rough in 24 fixtures in a seniors' residence wing. The company estimating guide allows 3.5 labour-hours per fixture, and the crew works 8-hour days. How many working days should the schedule allow?
- 42 days
- 10.5 days
- 5.25 days
- 2.6 days
Show the answer
C. Correct. 24 × 3.5 = 84 labour-hours; two workers × 8 h = 16 labour-hours per day; 84 ÷ 16 = 5.25 days. Rounding the schedule up to the next half or whole day leaves room for inspections and other trades.
Why not the others
A. 84 ÷ 2 = 42 is the labour-hours each worker puts in, not days. Dividing those 42 hours by an 8-hour day gives 5.25 days.
B. 84 ÷ 8 = 10.5 days is the time for one worker. With a crew of two the daily output doubles, so the job takes 5.25 days.
D. This divides 84 labour-hours by 32, counting the two workers twice. Two people working 8 hours supply 16 labour-hours a day, so 84 ÷ 16 = 5.25 days.
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Before entry to a sewage lift-station wet well, the monitor reads O₂ 20.9 %, LEL 0 % and H₂S 0 ppm at the hatch, and O₂ 20.8 %, LEL 0 % and H₂S 18 ppm when lowered to 0.5 m above the floor. The site's H₂S alarm is set at 10 ppm. What do these readings mean?
- The H₂S sensor is faulty, since the hatch reading was zero
- The space is safe; oxygen and LEL are normal at both levels
- Entry is fine with a particulate respirator fitted
- H₂S has pooled low; ventilate and retest before any entry
Show the answer
D. Correct. H₂S is heavier than air and collects near the bottom of pits and wet wells, so a clean reading at the hatch does not describe the work zone. Ventilate mechanically, retest at every level, and enter only under the confined-space permit once readings are within the program's limits, with an attendant and retrieval equipment in place.
Why not the others
A. A difference between levels is exactly what stratification looks like, because H₂S sinks. A bump test is good practice, but the readings are plausible and must be treated as real.
B. Normal oxygen and LEL do not make a space safe when a toxic gas is above its alarm point. 18 ppm of H₂S at the working level is above the 10 ppm alarm the site has set.
C. A particulate filter removes dust and aerosols, not gases. H₂S has to be cleared by ventilation, or entry made with supplied-air protection where the confined-space program allows it.
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Insulated 2-in (50 mm) copper heating pipes will pass through a suspended concrete slab under a mechanical room. The specification calls for sleeves that project 25 mm (1 in) above the finished floor. How are the sleeves installed?
- Fix sleeves sized to the bare pipe to the forms, flush with the floor
- Cast the pipe directly into the slab with no sleeve
- Core the slab after the pour, sized to the bare pipe
- Fix sleeves sized for pipe plus insulation to the forms, 25 mm proud
Show the answer
D. Correct. Sleeves are laid out from the drawings and fastened to the formwork before the pour, sized for the pipe plus its insulation and fire stopping, capped so concrete cannot fill them, and set to project above the floor so water on a mechanical-room floor cannot run down the penetration.
Why not the others
A. A sleeve sized to the bare pipe forces the insulation to stop at the slab, and a flush sleeve lets floor water run down the opening. The specification calls for room for insulation and a 25 mm projection.
B. Casting the pipe in prevents movement and future replacement and leaves no room for insulation. A sleeve allows expansion and a sealed, serviceable penetration.
C. Coring after the pour is the fallback when sleeves were missed; it risks cutting reinforcing and needs approval. Sized to the bare pipe it also leaves no room for insulation or fire stopping.
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | C | Installs piping supports |
| Q2 | B | Uses rigging, hoisting, lifting and positioning equipment |
| Q3 | C | Organizes project tasks and procedures |
| Q4 | D | Maintains safe work environment |
| Q5 | D | Installs piping sleeves |
03What block A covers
This block covers the skills every plumbing job depends on. It includes trench shoring and confined-space entry, PPE and fall protection, lock-out and tag-out, ladders and boom lifts, rigging and sling angles, brazing and hot-work permits, drawings, RFIs and as-builts, offsets and cut lengths, hangers, sleeves and fire stopping, water hammer, expansion and system commissioning.
The Red Seal Occupational Standard names this block “Performs common occupational skills”. It carries 11.2% of the exam, about 14 of the 125 questions, split across five tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Performs safety-related functions Maintains safe work environment; Uses personal protective equipment (PPE) and safety equipment; Performs lock-out and tag-out (LOTO) procedures | 19% |
| Uses and maintains tools and equipment Uses common tools and equipment; Uses access equipment; Uses rigging, hoisting, lifting and positioning equipment; Rigs loads for cranes; Uses welding equipment; Uses soldering and brazing equipment | 23% |
| Organizes work Organizes project tasks and procedures; Organizes materials and supplies; Uses documentation | 20% |
| Performs routine trade activities Plans layout for piping systems; Calculates tube, tubing and pipe lengths; Installs piping supports; Installs piping sleeves; Commissions systems; Protects piping systems, equipment and structure from damage; Coordinates excavation and backfilling of trenches; Installs fire stopping devices and materials | 34% |
| Uses communication and mentoring techniques Uses communication techniques; Uses mentoring techniques | 4% |
04What the questions turn on
Testing the air before entry
Test oxygen first, then flammable gas, then toxic gases, and test at the top, middle and bottom of the space. H2S is heavier than air and pools low, so a clean reading at the hatch says nothing about the floor.
Proving zero energy
After locking the valves and bleeding the section, close the drain and watch the gauge. A rise toward supply pressure with no temperature change means a valve is passing. Two locked valves with the drain between them locked open isolates it.
Offsets and cut lengths
For a 45° offset, travel is the offset times 1.414. On a rolling offset, find the true offset first as the square root of rise squared plus roll squared. Then subtract fitting take-offs, adding back thread engagement on threaded pipe.
Fire stopping matches the pipe
A fire-stop system is listed for one pipe material, size and assembly. Mineral wool and caulk listed for copper fails on ABS, which burns away. Plastic pipe needs a listed intumescent collar or wrap that swells and crushes the softening pipe shut.
05The other blocks
The 306A exam has seven blocks. Each has its own page of free questions:
The 306A Plumber practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.