Ontario On-Site Sewage Systems Technical Exam
Practice Questions & Verified Answers 2026
This specialized engineering preparation resource provides 300 targeted practice
questions and verified answers designed specifically for the Ontario On-Site Sewage
Systems technical qualification exam. It delivers comprehensive coverage of the Ontario
Building Code (OBC) Part 8, including soil percolation testing, design flows, septic tank
sizing, leaching bed layouts, and treatment unit technologies. Licensed designers,
installers, and building officials will master critical hydraulic calculations, soil
classification methods, and environmental compliance parameters to pass their
proctored Ministry certification.
QUESTION 1
Under the Ontario Building Code, which Part primarily addresses on-site sewage systems?
A. Part 3
B. Part 5
C. Part 8
D. Part 9
Answer: C. Part 8
Rationale: Part 8 of Division B contains the principal technical requirements for sewage
systems.
QUESTION 2
Which of the following is classified as a Class 1 sewage system?
A. Leaching bed
B. Greywater system
C. Cesspool
D. Composting toilet system
Answer: D. Composting toilet system
Rationale: Class 1 systems include composting toilets and various forms of privies and other
specified toilet systems.
,QUESTION 3
A greywater system is classified under which class?
A. Class 1
B. Class 2
C. Class 3
D. Class 4
_Answer: B. Class 2
Rationale: Ontario's Part 8 classification identifies greywater systems as Class 2 sewage
systems.
QUESTION 4
Which system is classified as Class 3?
A. Cesspool
B. Greywater system
C. Leaching bed
D. Holding tank
_Answer: A. Cesspool
Rationale: A cesspool is classified as a Class 3 sewage system.
QUESTION 5
A conventional leaching bed system is generally classified as:
A. Class 1
B. Class 2
C. Class 4
D. Class 5
_Answer: C. Class 4
Rationale: Class 4 systems include sewage systems using leaching beds.
,QUESTION 6
Which system is classified as Class 5?
A. Privy
B. Greywater system
C. Cesspool
D. Holding tank system for hauled sewage
_Answer: D. Holding tank system for hauled sewage
Rationale: A Class 5 system uses a holding tank to retain hauled sewage at the site before
collection.
QUESTION 7
The primary purpose of a sewage system is to:
A. Increase groundwater levels
B. Safely treat and/or dispose of sanitary sewage
C. Store drinking water
D. Eliminate the need for plumbing
_Answer: B. Safely treat and/or dispose of sanitary sewage
Rationale: Sewage systems are designed to manage sanitary sewage while protecting public
health and the environment.
QUESTION 8
Under the general limitation for sewage systems, a system is generally designed to receive:
A. Industrial chemicals
B. Stormwater only
C. Sanitary sewage of domestic origin
D. Petroleum products
_Answer: C. Sanitary sewage of domestic origin
Rationale: Part 8 generally limits sewage systems to sanitary sewage of domestic origin, subject
to specified exceptions.
, QUESTION 9
Which material should generally NOT be intentionally discharged into an on-site sewage
system?
A. Domestic wastewater
B. Toilet waste
C. Hazardous industrial chemicals
D. Domestic wash water
_Answer: C. Hazardous industrial chemicals
Rationale: Sewage systems are generally intended for sanitary sewage and are not designed to
safely manage hazardous industrial chemicals.
QUESTION 10
Which factor is particularly important when selecting a sewage system?
A. Property owner's favourite colour
B. Site conditions
C. Type of vehicle parked on the property
D. Exterior paint colour
_Answer: B. Site conditions
Rationale: Soil, groundwater, terrain, available area, sewage characteristics, and other site
conditions affect system selection and design.
DEFINITIONS AND BASIC PRINCIPLES
QUESTION 11
For purposes of Part 8, soil generally refers to naturally occurring unconsolidated material
capable of supporting:
A. Concrete
B. Plant growth
C. Vehicles
D. Buildings
_Answer: B. Plant growth
Practice Questions & Verified Answers 2026
This specialized engineering preparation resource provides 300 targeted practice
questions and verified answers designed specifically for the Ontario On-Site Sewage
Systems technical qualification exam. It delivers comprehensive coverage of the Ontario
Building Code (OBC) Part 8, including soil percolation testing, design flows, septic tank
sizing, leaching bed layouts, and treatment unit technologies. Licensed designers,
installers, and building officials will master critical hydraulic calculations, soil
classification methods, and environmental compliance parameters to pass their
proctored Ministry certification.
QUESTION 1
Under the Ontario Building Code, which Part primarily addresses on-site sewage systems?
A. Part 3
B. Part 5
C. Part 8
D. Part 9
Answer: C. Part 8
Rationale: Part 8 of Division B contains the principal technical requirements for sewage
systems.
QUESTION 2
Which of the following is classified as a Class 1 sewage system?
A. Leaching bed
B. Greywater system
C. Cesspool
D. Composting toilet system
Answer: D. Composting toilet system
Rationale: Class 1 systems include composting toilets and various forms of privies and other
specified toilet systems.
,QUESTION 3
A greywater system is classified under which class?
A. Class 1
B. Class 2
C. Class 3
D. Class 4
_Answer: B. Class 2
Rationale: Ontario's Part 8 classification identifies greywater systems as Class 2 sewage
systems.
QUESTION 4
Which system is classified as Class 3?
A. Cesspool
B. Greywater system
C. Leaching bed
D. Holding tank
_Answer: A. Cesspool
Rationale: A cesspool is classified as a Class 3 sewage system.
QUESTION 5
A conventional leaching bed system is generally classified as:
A. Class 1
B. Class 2
C. Class 4
D. Class 5
_Answer: C. Class 4
Rationale: Class 4 systems include sewage systems using leaching beds.
,QUESTION 6
Which system is classified as Class 5?
A. Privy
B. Greywater system
C. Cesspool
D. Holding tank system for hauled sewage
_Answer: D. Holding tank system for hauled sewage
Rationale: A Class 5 system uses a holding tank to retain hauled sewage at the site before
collection.
QUESTION 7
The primary purpose of a sewage system is to:
A. Increase groundwater levels
B. Safely treat and/or dispose of sanitary sewage
C. Store drinking water
D. Eliminate the need for plumbing
_Answer: B. Safely treat and/or dispose of sanitary sewage
Rationale: Sewage systems are designed to manage sanitary sewage while protecting public
health and the environment.
QUESTION 8
Under the general limitation for sewage systems, a system is generally designed to receive:
A. Industrial chemicals
B. Stormwater only
C. Sanitary sewage of domestic origin
D. Petroleum products
_Answer: C. Sanitary sewage of domestic origin
Rationale: Part 8 generally limits sewage systems to sanitary sewage of domestic origin, subject
to specified exceptions.
, QUESTION 9
Which material should generally NOT be intentionally discharged into an on-site sewage
system?
A. Domestic wastewater
B. Toilet waste
C. Hazardous industrial chemicals
D. Domestic wash water
_Answer: C. Hazardous industrial chemicals
Rationale: Sewage systems are generally intended for sanitary sewage and are not designed to
safely manage hazardous industrial chemicals.
QUESTION 10
Which factor is particularly important when selecting a sewage system?
A. Property owner's favourite colour
B. Site conditions
C. Type of vehicle parked on the property
D. Exterior paint colour
_Answer: B. Site conditions
Rationale: Soil, groundwater, terrain, available area, sewage characteristics, and other site
conditions affect system selection and design.
DEFINITIONS AND BASIC PRINCIPLES
QUESTION 11
For purposes of Part 8, soil generally refers to naturally occurring unconsolidated material
capable of supporting:
A. Concrete
B. Plant growth
C. Vehicles
D. Buildings
_Answer: B. Plant growth
