ONTARIO ON-SITE SEWAGE SYSTEMS TECHNICAL
EXAMINATION COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR JUST RELEASED
Exam Coverage — 10 Key Areas
1. Site evaluation and soil conditions — interpreting soil characteristics, groundwater, restrictive layers, slopes, and
available usable area.
2. Sewage system design principles — matching system capacity and configuration to anticipated sewage flows and site
limitations.
3. Class 1–5 sewage systems — recognizing system classifications and the circumstances in which different system types
are applicable.
4. Treatment tanks and components — understanding septic tanks, pumping chambers, treatment units, filters, alarms,
and related components.
5. Distribution systems — pressure distribution, gravity distribution, dosing arrangements, distribution boxes, and equal
loading.
6. Leaching beds and treatment areas — layout, infiltrative surfaces, distribution, replacement areas, and protection
from damage.
7. Setbacks and site protection — separation from buildings, wells, property features, water bodies, drainage, and other
constraints.
8. Construction and installation — excavation, bedding, pipe installation, compaction, backfilling, and protecting soil
structure.
9. Operation and maintenance — inspections, pumping, alarms, effluent filters, hydraulic overloading, and owner
responsibilities.
10. Code compliance and professional judgment — applying Part 8 requirements, approved treatment units, alternative
solutions, and identifying defective installations.
1. A proposed dwelling will use an on-site sewage system, but the site
has shallow restrictive soil and limited usable area. What should be
evaluated first before selecting the system configuration?
A. The colour of the proposed roof shingles
B. The site's soil, groundwater, and available treatment area
C. The number of electrical outlets inside the dwelling
D. The distance between bedrooms and exterior doors
Answer: B
Rationale: Proper sewage-system planning begins with site conditions
because soil, groundwater, available area, and restrictive features
determine feasible treatment and disposal options.
,2. During a site investigation, an installer discovers seasonal
groundwater significantly closer to the surface than originally
anticipated. Why is this discovery important?
A. It determines the home's electrical service size
B. It may reduce the available unsaturated soil needed for treatment
C. It automatically eliminates every type of sewage system
D. It changes the building's required window sizes
Answer: B
Rationale: Seasonal groundwater can reduce effective separation
beneath the treatment area, potentially affecting treatment
performance and system compliance.
3. A homeowner proposes placing a leaching bed beneath an area
where heavy vehicles will regularly travel. Why should the installer
reject this proposal?
A. Traffic can damage pipes and compact soil needed for infiltration
B. Vehicle weight increases household sewage production
C. Heavy vehicles always contaminate potable water supplies
D. Traffic automatically converts a Class 4 system into Class 5
Answer: A
Rationale: Vehicle loading can compact treatment soil and damage
buried components, reducing infiltration capacity and potentially
compromising long-term system performance.
,4. A septic tank is installed for a new residence, and the installer wants
to omit an effluent filter because the soil appears highly permeable.
What is the best response?
A. Highly permeable soil eliminates the need for all tank components
B. Components must comply with the applicable design and Building
Code requirements
C. Filters are prohibited for residential sewage systems
D. Filters are required only when the property contains a swimming
pool
Answer: B
Rationale: System components cannot be omitted based solely on soil
appearance; the applicable Building Code provisions and approved
design must be followed.
5. A distribution box is installed noticeably out of level, causing one
outlet to receive considerably more flow than another. What is the
primary concern?
A. Unequal wastewater loading across the treatment area
B. Increased roof drainage entering the building
C. Excessive electrical consumption by the dwelling
D. Increased household hot-water temperature
Answer: A
Rationale: Uneven distribution can overload portions of the treatment
area while leaving other portions underutilized, reducing treatment
effectiveness.
, 6. An installer is selecting a treatment unit for a sewage system where
enhanced treatment is required. What documentation should receive
particular attention?
A. The manufacturer's advertising brochure only
B. The unit's applicable approval and performance documentation
C. The homeowner's preferred landscaping plan
D. The local property's historical assessment notice
Answer: B
Rationale: Approved sewage treatment units must satisfy applicable
regulatory requirements, and the installer should verify approval
information and installation conditions.
7. Why is preserving natural soil structure particularly important when
constructing a conventional leaching bed?
A. Soil compaction can significantly reduce infiltration and treatment
performance
B. Soil compaction increases the household's water pressure
C. Soil disturbance eliminates the need for distribution piping
D. Soil structure only affects the property's landscaping appearance
Answer: A
Rationale: Treatment soil depends on appropriate pore structure for
movement, infiltration, and biological treatment, making unnecessary
compaction a serious concern.
EXAMINATION COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR JUST RELEASED
Exam Coverage — 10 Key Areas
1. Site evaluation and soil conditions — interpreting soil characteristics, groundwater, restrictive layers, slopes, and
available usable area.
2. Sewage system design principles — matching system capacity and configuration to anticipated sewage flows and site
limitations.
3. Class 1–5 sewage systems — recognizing system classifications and the circumstances in which different system types
are applicable.
4. Treatment tanks and components — understanding septic tanks, pumping chambers, treatment units, filters, alarms,
and related components.
5. Distribution systems — pressure distribution, gravity distribution, dosing arrangements, distribution boxes, and equal
loading.
6. Leaching beds and treatment areas — layout, infiltrative surfaces, distribution, replacement areas, and protection
from damage.
7. Setbacks and site protection — separation from buildings, wells, property features, water bodies, drainage, and other
constraints.
8. Construction and installation — excavation, bedding, pipe installation, compaction, backfilling, and protecting soil
structure.
9. Operation and maintenance — inspections, pumping, alarms, effluent filters, hydraulic overloading, and owner
responsibilities.
10. Code compliance and professional judgment — applying Part 8 requirements, approved treatment units, alternative
solutions, and identifying defective installations.
1. A proposed dwelling will use an on-site sewage system, but the site
has shallow restrictive soil and limited usable area. What should be
evaluated first before selecting the system configuration?
A. The colour of the proposed roof shingles
B. The site's soil, groundwater, and available treatment area
C. The number of electrical outlets inside the dwelling
D. The distance between bedrooms and exterior doors
Answer: B
Rationale: Proper sewage-system planning begins with site conditions
because soil, groundwater, available area, and restrictive features
determine feasible treatment and disposal options.
,2. During a site investigation, an installer discovers seasonal
groundwater significantly closer to the surface than originally
anticipated. Why is this discovery important?
A. It determines the home's electrical service size
B. It may reduce the available unsaturated soil needed for treatment
C. It automatically eliminates every type of sewage system
D. It changes the building's required window sizes
Answer: B
Rationale: Seasonal groundwater can reduce effective separation
beneath the treatment area, potentially affecting treatment
performance and system compliance.
3. A homeowner proposes placing a leaching bed beneath an area
where heavy vehicles will regularly travel. Why should the installer
reject this proposal?
A. Traffic can damage pipes and compact soil needed for infiltration
B. Vehicle weight increases household sewage production
C. Heavy vehicles always contaminate potable water supplies
D. Traffic automatically converts a Class 4 system into Class 5
Answer: A
Rationale: Vehicle loading can compact treatment soil and damage
buried components, reducing infiltration capacity and potentially
compromising long-term system performance.
,4. A septic tank is installed for a new residence, and the installer wants
to omit an effluent filter because the soil appears highly permeable.
What is the best response?
A. Highly permeable soil eliminates the need for all tank components
B. Components must comply with the applicable design and Building
Code requirements
C. Filters are prohibited for residential sewage systems
D. Filters are required only when the property contains a swimming
pool
Answer: B
Rationale: System components cannot be omitted based solely on soil
appearance; the applicable Building Code provisions and approved
design must be followed.
5. A distribution box is installed noticeably out of level, causing one
outlet to receive considerably more flow than another. What is the
primary concern?
A. Unequal wastewater loading across the treatment area
B. Increased roof drainage entering the building
C. Excessive electrical consumption by the dwelling
D. Increased household hot-water temperature
Answer: A
Rationale: Uneven distribution can overload portions of the treatment
area while leaving other portions underutilized, reducing treatment
effectiveness.
, 6. An installer is selecting a treatment unit for a sewage system where
enhanced treatment is required. What documentation should receive
particular attention?
A. The manufacturer's advertising brochure only
B. The unit's applicable approval and performance documentation
C. The homeowner's preferred landscaping plan
D. The local property's historical assessment notice
Answer: B
Rationale: Approved sewage treatment units must satisfy applicable
regulatory requirements, and the installer should verify approval
information and installation conditions.
7. Why is preserving natural soil structure particularly important when
constructing a conventional leaching bed?
A. Soil compaction can significantly reduce infiltration and treatment
performance
B. Soil compaction increases the household's water pressure
C. Soil disturbance eliminates the need for distribution piping
D. Soil structure only affects the property's landscaping appearance
Answer: A
Rationale: Treatment soil depends on appropriate pore structure for
movement, infiltration, and biological treatment, making unnecessary
compaction a serious concern.
