Alberta Plumber Apprenticeship
Certification Exam (Third Period) (Questions
and Correct Answers With Rationales)
Page 1 of 84
,Question 1: According to the National Plumbing Code of Canada (NPC),
what is the minimum required slope for a 3-inch horizontal drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
**CORRECT ANSWER: A. 1/8 inch per foot
Rationale: NPC Section 7.2.10.2 and Table 7.2.10.2.A dictate that horizontal
drainage piping 3 inches in diameter or larger must be sloped at a minimum
of 1/8 inch per foot (10 mm/m). Pipes 2.5 inches and smaller require a
minimum slope of 1/4 inch per foot (20 mm/m).
#Tags: #DWV #PipeSlope #NPCCode #AlbertaPlumber
Question 2: When installing a backwater valve in a building drain, what is
the MAXIMUM distance it can be located from the base of the soil stack it
is protecting?
A. 1 foot (300 mm)
B. 5 feet (1.5 m)
C. 10 feet (3 m)
D. There is no maximum distance, provided it is accessible
**CORRECT ANSWER: D. There is no maximum distance, provided it is
accessible
Rationale: The NPC does not specify a maximum distance for a backwater
valve from the stack base, but it mandates that the valve must be easily
accessible for inspection, cleaning, and maintenance (NPC 7.4.10.3). It is
typically installed as close to the building wall as possible on the building
side of the trap.
#Tags: #BackwaterValve #Drainage #Accessibility #NPCCode
Question 3: In a commercial kitchen, a grease interceptor is required.
According to the NPC, where must the grease interceptor be located?
Page 2 of 84
,A. Inside the kitchen, as close to the sink as possible
B. Outside the building, underground
C. Readily accessible for servicing and cleaning
D. In the basement, directly below the kitchen
**CORRECT ANSWER: C. Readily accessible for servicing and cleaning
Rationale: NPC 7.4.7.2 requires that grease interceptors be readily accessible.
While they can be located inside or outside, the primary code requirement
focuses on accessibility for regular pumping and maintenance. They must
not be buried under concrete or located in inaccessible crawlspaces.
#Tags: #GreaseInterceptor #CommercialPlumbing #Accessibility #NPCCode
Question 4: What is the MINIMUM size for a vent pipe serving a water
closet (toilet)?
A. 1.25 inches
B. 1.5 inches
C. 2 inches
D. 3 inches
**CORRECT ANSWER: B. 1.5 inches
Rationale: NPC Table 7.5.6.2 specifies the minimum vent pipe sizes based on
the fixture being served. A water closet requires a minimum vent size of 1.5
inches (38 mm), regardless of the trap size (which is typically 3" or 4").
#Tags: #Venting #WaterCloset #PipeSizing #NPCCode
Question 5: When sizing a building drain, you calculate the total Drainage
Fixture Units (DFU). If the total DFU is 540, what is the MINIMUM size
required for the building drain?
A. 3 inches
B. 4 inches
C. 5 inches
D. 6 inches
**CORRECT ANSWER: B. 4 inches
Page 3 of 84
, Rationale: According to NPC Table 7.2.10.3, a 4-inch building drain can
handle up to 540 DFU (at a slope of 1/8" per foot) or more at steeper slopes.
A 3-inch building drain is limited to a maximum of 27 DFU. Therefore, a 4-
inch pipe is the minimum required.
#Tags: #BuildingDrain #DFU #PipeSizing #NPCCode
Question 6: Which of the following devices is REQUIRED on a domestic hot
water storage tank to prevent excessive pressure buildup?
A. Pressure reducing valve (PRV)
B. Temperature and Pressure (T&P) relief valve
C. Vacuum relief valve
D. Check valve
**CORRECT ANSWER: B. Temperature and Pressure (T&P) relief valve
Rationale: NPC 7.6.2.5 and CSA B149.1 require that all hot water storage
tanks be equipped with an approved T&P relief valve. This valve will open if
the temperature exceeds 210°F (99°C) or the pressure exceeds the tank's
working pressure rating (usually 150 psi), preventing catastrophic tank
failure.
#Tags: #WaterHeater #SafetyDevices #TandPValve #NPCCode
Question 7: What is the MAXIMUM developed length allowed for a 1.5-
inch individual vent serving a single fixture, assuming the vent has no
bends?
A. 3 feet
B. 5 feet
C. 6 feet
D. It depends on the diameter of the fixture drain it serves
**CORRECT ANSWER: D. It depends on the diameter of the fixture drain it
serves
Rationale: NPC Table 7.5.6.3 dictates the maximum developed length of a
vent based on the diameter of the fixture drain it serves, not the diameter of
the vent itself. For example, a 1.5-inch vent serving a 1.25-inch fixture drain
can be up to 5 feet long, but if serving a 1.5-inch fixture drain, it can be up to
Page 4 of 84
Certification Exam (Third Period) (Questions
and Correct Answers With Rationales)
Page 1 of 84
,Question 1: According to the National Plumbing Code of Canada (NPC),
what is the minimum required slope for a 3-inch horizontal drainage pipe?
A. 1/8 inch per foot
B. 1/4 inch per foot
C. 1/2 inch per foot
D. 1 inch per foot
**CORRECT ANSWER: A. 1/8 inch per foot
Rationale: NPC Section 7.2.10.2 and Table 7.2.10.2.A dictate that horizontal
drainage piping 3 inches in diameter or larger must be sloped at a minimum
of 1/8 inch per foot (10 mm/m). Pipes 2.5 inches and smaller require a
minimum slope of 1/4 inch per foot (20 mm/m).
#Tags: #DWV #PipeSlope #NPCCode #AlbertaPlumber
Question 2: When installing a backwater valve in a building drain, what is
the MAXIMUM distance it can be located from the base of the soil stack it
is protecting?
A. 1 foot (300 mm)
B. 5 feet (1.5 m)
C. 10 feet (3 m)
D. There is no maximum distance, provided it is accessible
**CORRECT ANSWER: D. There is no maximum distance, provided it is
accessible
Rationale: The NPC does not specify a maximum distance for a backwater
valve from the stack base, but it mandates that the valve must be easily
accessible for inspection, cleaning, and maintenance (NPC 7.4.10.3). It is
typically installed as close to the building wall as possible on the building
side of the trap.
#Tags: #BackwaterValve #Drainage #Accessibility #NPCCode
Question 3: In a commercial kitchen, a grease interceptor is required.
According to the NPC, where must the grease interceptor be located?
Page 2 of 84
,A. Inside the kitchen, as close to the sink as possible
B. Outside the building, underground
C. Readily accessible for servicing and cleaning
D. In the basement, directly below the kitchen
**CORRECT ANSWER: C. Readily accessible for servicing and cleaning
Rationale: NPC 7.4.7.2 requires that grease interceptors be readily accessible.
While they can be located inside or outside, the primary code requirement
focuses on accessibility for regular pumping and maintenance. They must
not be buried under concrete or located in inaccessible crawlspaces.
#Tags: #GreaseInterceptor #CommercialPlumbing #Accessibility #NPCCode
Question 4: What is the MINIMUM size for a vent pipe serving a water
closet (toilet)?
A. 1.25 inches
B. 1.5 inches
C. 2 inches
D. 3 inches
**CORRECT ANSWER: B. 1.5 inches
Rationale: NPC Table 7.5.6.2 specifies the minimum vent pipe sizes based on
the fixture being served. A water closet requires a minimum vent size of 1.5
inches (38 mm), regardless of the trap size (which is typically 3" or 4").
#Tags: #Venting #WaterCloset #PipeSizing #NPCCode
Question 5: When sizing a building drain, you calculate the total Drainage
Fixture Units (DFU). If the total DFU is 540, what is the MINIMUM size
required for the building drain?
A. 3 inches
B. 4 inches
C. 5 inches
D. 6 inches
**CORRECT ANSWER: B. 4 inches
Page 3 of 84
, Rationale: According to NPC Table 7.2.10.3, a 4-inch building drain can
handle up to 540 DFU (at a slope of 1/8" per foot) or more at steeper slopes.
A 3-inch building drain is limited to a maximum of 27 DFU. Therefore, a 4-
inch pipe is the minimum required.
#Tags: #BuildingDrain #DFU #PipeSizing #NPCCode
Question 6: Which of the following devices is REQUIRED on a domestic hot
water storage tank to prevent excessive pressure buildup?
A. Pressure reducing valve (PRV)
B. Temperature and Pressure (T&P) relief valve
C. Vacuum relief valve
D. Check valve
**CORRECT ANSWER: B. Temperature and Pressure (T&P) relief valve
Rationale: NPC 7.6.2.5 and CSA B149.1 require that all hot water storage
tanks be equipped with an approved T&P relief valve. This valve will open if
the temperature exceeds 210°F (99°C) or the pressure exceeds the tank's
working pressure rating (usually 150 psi), preventing catastrophic tank
failure.
#Tags: #WaterHeater #SafetyDevices #TandPValve #NPCCode
Question 7: What is the MAXIMUM developed length allowed for a 1.5-
inch individual vent serving a single fixture, assuming the vent has no
bends?
A. 3 feet
B. 5 feet
C. 6 feet
D. It depends on the diameter of the fixture drain it serves
**CORRECT ANSWER: D. It depends on the diameter of the fixture drain it
serves
Rationale: NPC Table 7.5.6.3 dictates the maximum developed length of a
vent based on the diameter of the fixture drain it serves, not the diameter of
the vent itself. For example, a 1.5-inch vent serving a 1.25-inch fixture drain
can be up to 5 feet long, but if serving a 1.5-inch fixture drain, it can be up to
Page 4 of 84
