Ontario Building Code Sewage Systems
Exam 2026/2027 | 130 Questions on
Leaching Bed Design, Class 4 & 5,
Percolation Tests & Pressure Distribution
Description:
Master on-site sewage system certification with 130 exam-style questions updated for
2026/2027. Covers leaching beds, septic tanks, safety regulations, and Building Code
requirements.
Download the complete Q&A paper now to pass your installer or inspector exam on the first
attempt.
, Septic System Installer Exam 2026/2027
Section 1: Leaching Bed Design and Distribution
Question 1
Should the distribution pipes in a filter bed leaching bed be evenly spaced?
A. No, they should be clustered near the inlet
B. Yes, they should be evenly spaced
C. Only if the bed width exceeds 3 metres
D. No, spacing should decrease with distance from the inlet
Answer: B
Explanation: Even spacing of distribution pipes ensures uniform effluent distribution across
the entire filter bed area, preventing localized overloading and promoting consistent treatment
performance throughout the system.
Question 2
What is the required slope of the surface of the underlying stone layer in an absorption
trench?
A. Between 10 mm and 20 mm vertical drop for every 5 m of horizontal length
B. Between 30 mm and 50 mm vertical drop for every 10 m of horizontal length
C. Between 50 mm and 75 mm vertical drop for every 15 m of horizontal length
D. Level with no slope required
Answer: B
Explanation: A slope of 30 to 50 mm per 10 metres (0.3% to 0.5%) provides adequate
gravitational flow while preventing excessive velocity that could cause solids carryover or
uneven distribution.
Question 3
What is placed below and on top of the distribution pipes?
A. Pea gravel only
B. Septic stone
C. Filter fabric
D. Coarse sand
,Answer: B
Explanation: Septic stone (typically 20-50 mm washed gravel) provides structural support
for distribution pipes, creates storage void space for effluent, and allows uniform dispersal
into the underlying soil treatment area.
Question 4
Which dispersal bed type has a maximum bed width?
A. Type A
B. Type B
C. Type C
D. Type D
Answer: B
Explanation: Type B dispersal beds have specified maximum width limitations to ensure
proper distribution and treatment performance, distinguishing them from Type A beds which
have different dimensional requirements.
Question 5
Which dispersal bed type can be installed in slopes up to 25%?
A. Type A
B. Type B
C. Type C
D. Type D
Answer: A
Explanation: Type A dispersal beds are specifically designed for sloped applications and
may be installed on grades up to 25%, provided appropriate construction techniques are
employed to maintain bed integrity.
Question 6
Where the underlying soil has a percolation time of 20 minutes per centimetre, what is the
minimum area of a Type B dispersal bed if the total daily design flow is 1,600 L?
A. 60 m²
B. 70 m²
, C. 80 m²
D. 90 m²
Answer: C
Explanation: The minimum bed area is calculated using the design flow divided by the
allowable loading rate. For a percolation time of 20 min/cm, the loading rate is 20 L/d/m²,
resulting in 1,600 ÷ 20 = 80 m².
Question 7
Which dispersal bed type requires pressure distribution?
A. Type A only
B. Type B only
C. Both Type A and Type B
D. Neither Type A nor Type B
Answer: B
Explanation: Type B dispersal beds require pressurized distribution to ensure uniform
effluent delivery across the bed area, as gravity distribution alone cannot achieve the
necessary even application rates.
Section 2: Installation Practices and Backfill Requirements
Question 8
What should be left uncovered after installing a sewage system and before placing the
backfill and topsoil?
A. Distribution boxes and header pipes only
B. Perforated distribution pipes only
C. Bottom end of the leaching bed only
D. Distribution boxes, header pipes, and perforated distribution pipes
Answer: D
Explanation: Distribution boxes, header pipes, and perforated distribution pipes must remain
exposed for inspection to verify proper installation, alignment, and connections before
backfill operations commence.
Exam 2026/2027 | 130 Questions on
Leaching Bed Design, Class 4 & 5,
Percolation Tests & Pressure Distribution
Description:
Master on-site sewage system certification with 130 exam-style questions updated for
2026/2027. Covers leaching beds, septic tanks, safety regulations, and Building Code
requirements.
Download the complete Q&A paper now to pass your installer or inspector exam on the first
attempt.
, Septic System Installer Exam 2026/2027
Section 1: Leaching Bed Design and Distribution
Question 1
Should the distribution pipes in a filter bed leaching bed be evenly spaced?
A. No, they should be clustered near the inlet
B. Yes, they should be evenly spaced
C. Only if the bed width exceeds 3 metres
D. No, spacing should decrease with distance from the inlet
Answer: B
Explanation: Even spacing of distribution pipes ensures uniform effluent distribution across
the entire filter bed area, preventing localized overloading and promoting consistent treatment
performance throughout the system.
Question 2
What is the required slope of the surface of the underlying stone layer in an absorption
trench?
A. Between 10 mm and 20 mm vertical drop for every 5 m of horizontal length
B. Between 30 mm and 50 mm vertical drop for every 10 m of horizontal length
C. Between 50 mm and 75 mm vertical drop for every 15 m of horizontal length
D. Level with no slope required
Answer: B
Explanation: A slope of 30 to 50 mm per 10 metres (0.3% to 0.5%) provides adequate
gravitational flow while preventing excessive velocity that could cause solids carryover or
uneven distribution.
Question 3
What is placed below and on top of the distribution pipes?
A. Pea gravel only
B. Septic stone
C. Filter fabric
D. Coarse sand
,Answer: B
Explanation: Septic stone (typically 20-50 mm washed gravel) provides structural support
for distribution pipes, creates storage void space for effluent, and allows uniform dispersal
into the underlying soil treatment area.
Question 4
Which dispersal bed type has a maximum bed width?
A. Type A
B. Type B
C. Type C
D. Type D
Answer: B
Explanation: Type B dispersal beds have specified maximum width limitations to ensure
proper distribution and treatment performance, distinguishing them from Type A beds which
have different dimensional requirements.
Question 5
Which dispersal bed type can be installed in slopes up to 25%?
A. Type A
B. Type B
C. Type C
D. Type D
Answer: A
Explanation: Type A dispersal beds are specifically designed for sloped applications and
may be installed on grades up to 25%, provided appropriate construction techniques are
employed to maintain bed integrity.
Question 6
Where the underlying soil has a percolation time of 20 minutes per centimetre, what is the
minimum area of a Type B dispersal bed if the total daily design flow is 1,600 L?
A. 60 m²
B. 70 m²
, C. 80 m²
D. 90 m²
Answer: C
Explanation: The minimum bed area is calculated using the design flow divided by the
allowable loading rate. For a percolation time of 20 min/cm, the loading rate is 20 L/d/m²,
resulting in 1,600 ÷ 20 = 80 m².
Question 7
Which dispersal bed type requires pressure distribution?
A. Type A only
B. Type B only
C. Both Type A and Type B
D. Neither Type A nor Type B
Answer: B
Explanation: Type B dispersal beds require pressurized distribution to ensure uniform
effluent delivery across the bed area, as gravity distribution alone cannot achieve the
necessary even application rates.
Section 2: Installation Practices and Backfill Requirements
Question 8
What should be left uncovered after installing a sewage system and before placing the
backfill and topsoil?
A. Distribution boxes and header pipes only
B. Perforated distribution pipes only
C. Bottom end of the leaching bed only
D. Distribution boxes, header pipes, and perforated distribution pipes
Answer: D
Explanation: Distribution boxes, header pipes, and perforated distribution pipes must remain
exposed for inspection to verify proper installation, alignment, and connections before
backfill operations commence.
