Ontario Plumber Licensing Exam – Practice
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1. What is the minimum size of a building drain for a single dwelling?
A. 2 in.
B. 3 in.
C. 4 in.
D. 5 in.
The Code requires a minimum 4-inch building drain for a single
dwelling.
2. A cleanout must be installed at the base of every soil stack
because:
A. It reduces noise transmission.
B. It allows access for clearing blockages.
C. It supports the stack structurally.
D. It reduces friction loss.
Cleanouts provide access to remove clogs for maintenance.
3. What is the maximum horizontal distance between vent pipe
supports?
A. 4 ft
B. 6 ft
C. 8 ft
, D. 10 ft
Vent pipes typically require supports every 10 f t horizontally.
4. A trap seal must be at least:
A. 1/2 in.
B. 1 in.
C. 2 in.
D. 3 in.
Most codes require a minimum trap seal of 2 inches to prevent
sewer gases entering the building.
5. What type of piping is prohibited for potable water in Ontario?
A. Copper
B. PEX
C. CPVC
D. Lead
Lead piping is banned due to health hazards.
6. The purpose of a vent pipe is to:
A. Increase water pressure
B. Equalize air pressure in the drainage system
C. Heat drainpipes
D. Remove solids
Vents prevent siphonage and allow proper flow.
7. Backflow prevention is required to prevent:
A. Water hammer
B. Contamination of potable water
C. Leaking traps
D. Stormwater entry
, Backflow devices stop pollutants from entering drinking water
systems.
8. What is the minimum slope for a horizontal 3-inch drainage line?
A. 1%
B. 1/8 in/ft
C. 1/4 in/ft
D. 1/2 in/ft
3-inch drains require a minimum 1/4 in/ft slope to maintain flow.
9. The main water shutoff valve must be located:
A. At the highest fixture
B. As close as possible to where the service enters the building
C. Beside the floor drain
D. Next to the water heater
It must be accessible and near the service entry.
10. A wet vent is permitted to vent:
A. Kitchen sinks
B. Bathroom groups
C. Laundry rooms
D. Exterior drains
Ontario permits wet venting for bathroom groups under specific
conditions.
11. What material is commonly used for below-ground sanitary
services?
A. ABS
B. Copper
C. PVC SDR-28 or SDR-35
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the minimum size of a building drain for a single dwelling?
A. 2 in.
B. 3 in.
C. 4 in.
D. 5 in.
The Code requires a minimum 4-inch building drain for a single
dwelling.
2. A cleanout must be installed at the base of every soil stack
because:
A. It reduces noise transmission.
B. It allows access for clearing blockages.
C. It supports the stack structurally.
D. It reduces friction loss.
Cleanouts provide access to remove clogs for maintenance.
3. What is the maximum horizontal distance between vent pipe
supports?
A. 4 ft
B. 6 ft
C. 8 ft
, D. 10 ft
Vent pipes typically require supports every 10 f t horizontally.
4. A trap seal must be at least:
A. 1/2 in.
B. 1 in.
C. 2 in.
D. 3 in.
Most codes require a minimum trap seal of 2 inches to prevent
sewer gases entering the building.
5. What type of piping is prohibited for potable water in Ontario?
A. Copper
B. PEX
C. CPVC
D. Lead
Lead piping is banned due to health hazards.
6. The purpose of a vent pipe is to:
A. Increase water pressure
B. Equalize air pressure in the drainage system
C. Heat drainpipes
D. Remove solids
Vents prevent siphonage and allow proper flow.
7. Backflow prevention is required to prevent:
A. Water hammer
B. Contamination of potable water
C. Leaking traps
D. Stormwater entry
, Backflow devices stop pollutants from entering drinking water
systems.
8. What is the minimum slope for a horizontal 3-inch drainage line?
A. 1%
B. 1/8 in/ft
C. 1/4 in/ft
D. 1/2 in/ft
3-inch drains require a minimum 1/4 in/ft slope to maintain flow.
9. The main water shutoff valve must be located:
A. At the highest fixture
B. As close as possible to where the service enters the building
C. Beside the floor drain
D. Next to the water heater
It must be accessible and near the service entry.
10. A wet vent is permitted to vent:
A. Kitchen sinks
B. Bathroom groups
C. Laundry rooms
D. Exterior drains
Ontario permits wet venting for bathroom groups under specific
conditions.
11. What material is commonly used for below-ground sanitary
services?
A. ABS
B. Copper
C. PVC SDR-28 or SDR-35
