Alberta Plumber Apprenticeship Certification Exam
Questions and Correct Answers
Question 1: According to the National Plumbing Code of Canada, what is the MINIMUM trap
seal depth required for a plumbing fixture trap?
A. 25 mm (1 inch)
B. 50 mm (2 inches)
C. 75 mm (3 inches)
D. 100 mm (4 inches)
CORRECT ANSWER: B. 50 mm (2 inches)
Rationale: National Plumbing Code of Canada (NPCC) Section 2.2.2.1 requires that every trap
shall have a water seal of not less than 50 mm (2 inches) and not more than 100 mm (4 inches).
This depth prevents sewer gases from entering the building while allowing proper drainage.
Option A is insufficient to prevent gas passage. Options C and D exceed the maximum allowable
seal depth, which can cause siphonage and trap seal loss.
Question 2: A plumber is installing a water closet in a residential bathroom. According to NPCC,
what is the MAXIMUM distance a vent pipe can be from the trap weir of the water closet?
A. 1.5 m (5 ft)
B. 3.0 m (10 ft)
C. 4.5 m (15 ft)
D. 6.0 m (20 ft)
CORRECT ANSWER: B. 3.0 m (10 ft)
Rationale: NPCC Table 2.2.3.1 specifies maximum distances between trap and vent. For a water
closet (4-inch fixture drain), the maximum distance from trap weir to vent is 3.0 m (10 ft). This
prevents trap siphonage and ensures proper drainage. Option A is too restrictive. Options C and
D exceed code limits and would require a re-vent or circuit vent.
Question 3: Which pipe material is PERMITTED for underground water service lines in Alberta
according to the Plumbing Regulation?
A. Polybutylene (PB)
B. Cross-linked polyethylene (PEX)
C. Copper Type M
D. PVC Schedule 40
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,CORRECT ANSWER: B. Cross-linked polyethylene (PEX)
Rationale: Alberta Plumbing Regulation and NPCC Section 2.6 permit PEX tubing for
underground water services when listed for direct burial and protected from physical damage.
Polybutylene (A) is prohibited due to failure history. Copper Type M (C) is permitted but requires
corrosion protection underground. PVC Schedule 40 (D) is not approved for potable water
pressure applications in Alberta.
Question 4: When installing a horizontal drainage pipe, what is the MINIMUM slope required for
a 3-inch pipe according to NPCC?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
CORRECT ANSWER: B. 1/8 inch per foot
Rationale: NPCC Table 2.4.10.3 specifies minimum slopes for horizontal drainage piping. For
pipe sizes 3 inches and larger, the minimum slope is 1/8 inch per foot (1%). Smaller pipes (1¼-2
inch) require ¼ inch per foot. Option A is insufficient for self-scouring velocity. Options C and D
exceed minimum requirements but may be used where space permits.
Question 5: Which type of valve is REQUIRED on the water supply line to a water heater
according to NPCC?
A. Gate valve
B. Ball valve
C. Pressure relief valve
D. Check valve
CORRECT ANSWER: C. Pressure relief valve
Rationale: NPCC Section 2.6.3.1 requires every water heater to be protected by a temperature
and pressure relief valve (T&P valve) to prevent catastrophic failure from over-temperature or
over-pressure conditions. Gate (A) and ball valves (B) are shut-off valves, not safety devices.
Check valves (D) prevent backflow but do not relieve pressure.
Question 6: A plumber is joining copper tubing using soldered joints. According to CSA B125,
what is the MINIMUM overlap required for a soldered cup joint?
A. Equal to the tube diameter
B. ½ the tube diameter
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,C. ¾ the tube diameter
D. Twice the tube diameter
CORRECT ANSWER: A. Equal to the tube diameter
Rationale: CSA B125.3 and plumbing best practices require that soldered cup joints have a
minimum engagement (overlap) equal to the tube diameter to ensure a strong, leak-free joint.
Option B is insufficient for joint strength. Options C and D exceed minimum requirements but
are not code-mandated.
Question 7: According to Alberta Occupational Health and Safety, what is the MINIMUM oxygen
concentration required in a confined space before entry?
A. 18.0%
B. 19.5%
C. 20.9%
D. 23.5%
CORRECT ANSWER: B. 19.5%
Rationale: Alberta OHS Code Part 5 (Confined Spaces) requires atmospheric testing before entry.
The acceptable oxygen concentration range is 19.5% to 23.0%. Below 19.5% is oxygen-deficient
and requires ventilation or respiratory protection. Option A is below the safe threshold. Option
C is normal atmospheric concentration. Option D is the upper limit before oxygen-enriched
hazards occur.
Question 8: What is the CORRECT formula for calculating the travel length of a 45-degree offset
in piping?
A. Travel = Offset × 1.414
B. Travel = Offset × 2.0
C. Travel = Offset × 0.707
D. Travel = Offset × 1.0
CORRECT ANSWER: A. Travel = Offset × 1.414
Rationale: For a 45-degree offset, the travel (diagonal pipe length) equals the offset multiplied
by the cosecant of 45°, which is 1.414 (√2). This is a fundamental plumbing calculation for
pipefitting. Option B applies to 90-degree offsets. Option C is the sine of 45°, used for different
calculations. Option D would only apply if the offset and travel were equal, which is not
geometrically correct for 45°.
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, Question 9: According to NPCC, which of the following fixtures requires an individual vent?
A. Water closet
B. Lavatory
C. Kitchen sink
D. Bathtub
CORRECT ANSWER: A. Water closet
Rationale: NPCC Section 2.2.3 requires water closets to be individually vented or connected to a
circuit vent due to their large waste volume and potential for siphonage. Lavatories (B), kitchen
sinks (C), and bathtubs (D) may be wet-vented or circuit-vented with other fixtures under
specific conditions.
Question 10: A plumber is installing a floor drain in a basement. According to NPCC, what is the
MINIMUM trap size required for a floor drain?
A. 1¼ inches
B. 1½ inches
C. 2 inches
D. 3 inches
CORRECT ANSWER: C. 2 inches
Rationale: NPCC Table 2.2.2.2 specifies minimum trap sizes. Floor drains require a minimum 2-
inch trap and drain to handle potential solids and prevent clogging. Options A and B are for
smaller fixtures like lavatories. Option D is for larger fixtures like water closets but is not the
minimum for floor drains.
Question 11: Which type of pipe support is REQUIRED for horizontal copper water piping at
intervals NOT exceeding?
A. 1.2 m (4 ft)
B. 1.8 m (6 ft)
C. 2.4 m (8 ft)
D. 3.0 m (10 ft)
CORRECT ANSWER: B. 1.8 m (6 ft)
Rationale: NPCC Table 2.6.2.1 specifies support spacing for piping. For horizontal copper water
tubing 1 inch and smaller, supports are required at intervals not exceeding 1.8 m (6 ft). Larger
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Questions and Correct Answers
Question 1: According to the National Plumbing Code of Canada, what is the MINIMUM trap
seal depth required for a plumbing fixture trap?
A. 25 mm (1 inch)
B. 50 mm (2 inches)
C. 75 mm (3 inches)
D. 100 mm (4 inches)
CORRECT ANSWER: B. 50 mm (2 inches)
Rationale: National Plumbing Code of Canada (NPCC) Section 2.2.2.1 requires that every trap
shall have a water seal of not less than 50 mm (2 inches) and not more than 100 mm (4 inches).
This depth prevents sewer gases from entering the building while allowing proper drainage.
Option A is insufficient to prevent gas passage. Options C and D exceed the maximum allowable
seal depth, which can cause siphonage and trap seal loss.
Question 2: A plumber is installing a water closet in a residential bathroom. According to NPCC,
what is the MAXIMUM distance a vent pipe can be from the trap weir of the water closet?
A. 1.5 m (5 ft)
B. 3.0 m (10 ft)
C. 4.5 m (15 ft)
D. 6.0 m (20 ft)
CORRECT ANSWER: B. 3.0 m (10 ft)
Rationale: NPCC Table 2.2.3.1 specifies maximum distances between trap and vent. For a water
closet (4-inch fixture drain), the maximum distance from trap weir to vent is 3.0 m (10 ft). This
prevents trap siphonage and ensures proper drainage. Option A is too restrictive. Options C and
D exceed code limits and would require a re-vent or circuit vent.
Question 3: Which pipe material is PERMITTED for underground water service lines in Alberta
according to the Plumbing Regulation?
A. Polybutylene (PB)
B. Cross-linked polyethylene (PEX)
C. Copper Type M
D. PVC Schedule 40
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,CORRECT ANSWER: B. Cross-linked polyethylene (PEX)
Rationale: Alberta Plumbing Regulation and NPCC Section 2.6 permit PEX tubing for
underground water services when listed for direct burial and protected from physical damage.
Polybutylene (A) is prohibited due to failure history. Copper Type M (C) is permitted but requires
corrosion protection underground. PVC Schedule 40 (D) is not approved for potable water
pressure applications in Alberta.
Question 4: When installing a horizontal drainage pipe, what is the MINIMUM slope required for
a 3-inch pipe according to NPCC?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
CORRECT ANSWER: B. 1/8 inch per foot
Rationale: NPCC Table 2.4.10.3 specifies minimum slopes for horizontal drainage piping. For
pipe sizes 3 inches and larger, the minimum slope is 1/8 inch per foot (1%). Smaller pipes (1¼-2
inch) require ¼ inch per foot. Option A is insufficient for self-scouring velocity. Options C and D
exceed minimum requirements but may be used where space permits.
Question 5: Which type of valve is REQUIRED on the water supply line to a water heater
according to NPCC?
A. Gate valve
B. Ball valve
C. Pressure relief valve
D. Check valve
CORRECT ANSWER: C. Pressure relief valve
Rationale: NPCC Section 2.6.3.1 requires every water heater to be protected by a temperature
and pressure relief valve (T&P valve) to prevent catastrophic failure from over-temperature or
over-pressure conditions. Gate (A) and ball valves (B) are shut-off valves, not safety devices.
Check valves (D) prevent backflow but do not relieve pressure.
Question 6: A plumber is joining copper tubing using soldered joints. According to CSA B125,
what is the MINIMUM overlap required for a soldered cup joint?
A. Equal to the tube diameter
B. ½ the tube diameter
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,C. ¾ the tube diameter
D. Twice the tube diameter
CORRECT ANSWER: A. Equal to the tube diameter
Rationale: CSA B125.3 and plumbing best practices require that soldered cup joints have a
minimum engagement (overlap) equal to the tube diameter to ensure a strong, leak-free joint.
Option B is insufficient for joint strength. Options C and D exceed minimum requirements but
are not code-mandated.
Question 7: According to Alberta Occupational Health and Safety, what is the MINIMUM oxygen
concentration required in a confined space before entry?
A. 18.0%
B. 19.5%
C. 20.9%
D. 23.5%
CORRECT ANSWER: B. 19.5%
Rationale: Alberta OHS Code Part 5 (Confined Spaces) requires atmospheric testing before entry.
The acceptable oxygen concentration range is 19.5% to 23.0%. Below 19.5% is oxygen-deficient
and requires ventilation or respiratory protection. Option A is below the safe threshold. Option
C is normal atmospheric concentration. Option D is the upper limit before oxygen-enriched
hazards occur.
Question 8: What is the CORRECT formula for calculating the travel length of a 45-degree offset
in piping?
A. Travel = Offset × 1.414
B. Travel = Offset × 2.0
C. Travel = Offset × 0.707
D. Travel = Offset × 1.0
CORRECT ANSWER: A. Travel = Offset × 1.414
Rationale: For a 45-degree offset, the travel (diagonal pipe length) equals the offset multiplied
by the cosecant of 45°, which is 1.414 (√2). This is a fundamental plumbing calculation for
pipefitting. Option B applies to 90-degree offsets. Option C is the sine of 45°, used for different
calculations. Option D would only apply if the offset and travel were equal, which is not
geometrically correct for 45°.
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, Question 9: According to NPCC, which of the following fixtures requires an individual vent?
A. Water closet
B. Lavatory
C. Kitchen sink
D. Bathtub
CORRECT ANSWER: A. Water closet
Rationale: NPCC Section 2.2.3 requires water closets to be individually vented or connected to a
circuit vent due to their large waste volume and potential for siphonage. Lavatories (B), kitchen
sinks (C), and bathtubs (D) may be wet-vented or circuit-vented with other fixtures under
specific conditions.
Question 10: A plumber is installing a floor drain in a basement. According to NPCC, what is the
MINIMUM trap size required for a floor drain?
A. 1¼ inches
B. 1½ inches
C. 2 inches
D. 3 inches
CORRECT ANSWER: C. 2 inches
Rationale: NPCC Table 2.2.2.2 specifies minimum trap sizes. Floor drains require a minimum 2-
inch trap and drain to handle potential solids and prevent clogging. Options A and B are for
smaller fixtures like lavatories. Option D is for larger fixtures like water closets but is not the
minimum for floor drains.
Question 11: Which type of pipe support is REQUIRED for horizontal copper water piping at
intervals NOT exceeding?
A. 1.2 m (4 ft)
B. 1.8 m (6 ft)
C. 2.4 m (8 ft)
D. 3.0 m (10 ft)
CORRECT ANSWER: B. 1.8 m (6 ft)
Rationale: NPCC Table 2.6.2.1 specifies support spacing for piping. For horizontal copper water
tubing 1 inch and smaller, supports are required at intervals not exceeding 1.8 m (6 ft). Larger
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