Ontario Plumber Licensing Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. What is the minimum pipe size for a water service supplying a
single-family dwelling?
A. 15 mm
B. 20 mm
C. 25 mm
D. 32 mm
B. 20 mm
The Ontario Plumbing Code requires a minimum 20 mm pipe for
single-family dwelling water service to ensure adequate flow and
pressure.
2. Which of the following materials is approved for potable water
distribution in Ontario?
A. PVC Schedule 40
B. CPVC
C. Lead
D. Galvanized steel
B. CPVC
CPVC is approved for potable water systems in Ontario due to its
corrosion resistance and safety for drinking water.
,3. What is the maximum slope for a horizontal drain pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
C. 1/4 inch per foot
Drainage pipes must slope at least 1/4 inch per foot to allow
proper gravity flow and prevent clogging.
4. What is the minimum vent size for a 1-1/2 inch drain?
A. 1 inch
B. 1-1/4 inch
C. 1-1/2 inch
D. 2 inch
A. 1 inch
Vents must be sized to prevent siphoning of traps; a 1-inch vent is
sufficient for a 1-1/2 inch drain.
5. Which of the following fittings is prohibited for underground
potable water piping?
A. Copper soldered
B. Lead
C. PEX
D. PVC Schedule 40
B. Lead
Lead pipes are prohibited for potable water due to toxicity
concerns.
6. What is the maximum allowable distance from a trap to a vent for
a 2-inch drain pipe?
, A. 3 feet
B. 5 feet
C. 6 feet
D. 8 feet
C. 6 feet
The Ontario Plumbing Code sets maximum trap arm lengths to
maintain proper venting and prevent siphoning.
7. Which method is acceptable for joining PVC pipe for drainage?
A. Threaded connections
B. Solvent cement
C. Welding
D. Compression fitting
B. Solvent cement
PVC drainage pipes are joined with solvent cement, which
chemically fuses the pipes.
8. What is the minimum fixture unit load for a water closet in a
private residence?
A. 1.0
B. 2.0
C. 3.0
D. 4.0
C. 3.0
Fixture unit values are standardized in the Plumbing Code; a
residential water closet is 3 fixture units.
9. What is the primary purpose of a trap?
A. Increase water pressure
B. Prevent sewer gases from entering the building
, C. Filter debris
D. Act as a water meter
B. Prevent sewer gases from entering the building
Traps create a water seal that blocks sewer gases from entering
living spaces.
10. What is the minimum thickness of copper tubing for Type L
water distribution piping?
A. 0.032 inches
B. 0.040 inches
C. 0.050 inches
D. 0.065 inches
B. 0.040 inches
Type L copper has a standard wall thickness of 0.040 inches for
durability and pressure handling.
11. When is a backflow preventer required?
A. On all cold water lines
B. When cross-connection is possible
C. Only on hot water lines
D. Only in industrial buildings
B. When cross-connection is possible
Backflow preventers protect potable water from contamination in
case of a cross-connection.
12. What is the maximum water pressure allowed in a
residential plumbing system in Ontario?
A. 40 psi
B. 50 psi
C. 80 psi
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the minimum pipe size for a water service supplying a
single-family dwelling?
A. 15 mm
B. 20 mm
C. 25 mm
D. 32 mm
B. 20 mm
The Ontario Plumbing Code requires a minimum 20 mm pipe for
single-family dwelling water service to ensure adequate flow and
pressure.
2. Which of the following materials is approved for potable water
distribution in Ontario?
A. PVC Schedule 40
B. CPVC
C. Lead
D. Galvanized steel
B. CPVC
CPVC is approved for potable water systems in Ontario due to its
corrosion resistance and safety for drinking water.
,3. What is the maximum slope for a horizontal drain pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
C. 1/4 inch per foot
Drainage pipes must slope at least 1/4 inch per foot to allow
proper gravity flow and prevent clogging.
4. What is the minimum vent size for a 1-1/2 inch drain?
A. 1 inch
B. 1-1/4 inch
C. 1-1/2 inch
D. 2 inch
A. 1 inch
Vents must be sized to prevent siphoning of traps; a 1-inch vent is
sufficient for a 1-1/2 inch drain.
5. Which of the following fittings is prohibited for underground
potable water piping?
A. Copper soldered
B. Lead
C. PEX
D. PVC Schedule 40
B. Lead
Lead pipes are prohibited for potable water due to toxicity
concerns.
6. What is the maximum allowable distance from a trap to a vent for
a 2-inch drain pipe?
, A. 3 feet
B. 5 feet
C. 6 feet
D. 8 feet
C. 6 feet
The Ontario Plumbing Code sets maximum trap arm lengths to
maintain proper venting and prevent siphoning.
7. Which method is acceptable for joining PVC pipe for drainage?
A. Threaded connections
B. Solvent cement
C. Welding
D. Compression fitting
B. Solvent cement
PVC drainage pipes are joined with solvent cement, which
chemically fuses the pipes.
8. What is the minimum fixture unit load for a water closet in a
private residence?
A. 1.0
B. 2.0
C. 3.0
D. 4.0
C. 3.0
Fixture unit values are standardized in the Plumbing Code; a
residential water closet is 3 fixture units.
9. What is the primary purpose of a trap?
A. Increase water pressure
B. Prevent sewer gases from entering the building
, C. Filter debris
D. Act as a water meter
B. Prevent sewer gases from entering the building
Traps create a water seal that blocks sewer gases from entering
living spaces.
10. What is the minimum thickness of copper tubing for Type L
water distribution piping?
A. 0.032 inches
B. 0.040 inches
C. 0.050 inches
D. 0.065 inches
B. 0.040 inches
Type L copper has a standard wall thickness of 0.040 inches for
durability and pressure handling.
11. When is a backflow preventer required?
A. On all cold water lines
B. When cross-connection is possible
C. Only on hot water lines
D. Only in industrial buildings
B. When cross-connection is possible
Backflow preventers protect potable water from contamination in
case of a cross-connection.
12. What is the maximum water pressure allowed in a
residential plumbing system in Ontario?
A. 40 psi
B. 50 psi
C. 80 psi
