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100+ Free OBC On-site Sewage Systems Practice Questions

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2026 Statistics

Key Facts: OBC On-site Sewage Systems Exam

100

Practice Questions

Antigravity Exam Bank

3.0 hrs

Exam Duration

Humber/MMAH

70%

Passing Mark

Humber/MMAH

$150 CAD

Exam Fee

Humber/MMAH

Open Book

Exam Format

2024 OBC Compendium

A 3.0-hour open-book exam administered by Humber College for MMAH qualification, covering Part 8 sewage classifications, septic tank sizing, leaching beds, soil percolation time tests, and clearances. A passing score of 70% is required.

Sample OBC On-site Sewage Systems Practice Questions

Try these sample questions to test your OBC On-site Sewage Systems exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which class of sewage system under the Ontario Building Code refers specifically to a greywater system?
A.Class 1
B.Class 2
C.Class 3
D.Class 4
Explanation: According to Article 8.1.2.1. of the Ontario Building Code, a Class 2 sewage system is defined as a greywater system. Greywater systems are designed exclusively for the treatment and disposal of greywater where the daily design flow is less than 1,000 L/day.
2Under OBC Part 8, what type of sewage system is classified as a Class 3 system?
A.Cesspool
B.Holding tank
C.Greywater system
D.Outhouse/Privy
Explanation: Article 8.1.2.1. of the Ontario Building Code classifies a cesspool as a Class 3 sewage system. Cesspools are designed to receive waste only from a Class 1 system (such as a privy) and are limited to daily design flows of less than 1,000 L/day.
3What is the classification of a sewage system consisting of a septic tank and a leaching bed?
A.Class 2
B.Class 3
C.Class 4
D.Class 5
Explanation: Under Article 8.1.2.1., a Class 4 sewage system consists of a treatment unit (such as a septic tank) and a leaching bed (such as absorption trenches or a filter bed). This is the standard soil-based treatment system for residential homes.
4Which of the following is classified as a Class 1 sewage system under the Ontario Building Code?
A.A chemical toilet or composting toilet
B.A greywater leaching pit
C.A septic tank with an absorption trench
D.A holding tank requiring regular pump-outs
Explanation: According to Section 8.1.2., Class 1 systems are waterless closets including composting toilets, chemical toilets, incinerating toilets, and privies. They do not discharge liquid effluent into the ground.
5What is the base daily design sanitary sewage flow (Q) for a 3-bedroom residential dwelling under the OBC?
A.750 L/day
B.1,100 L/day
C.1,600 L/day
D.2,000 L/day
Explanation: Table 8.2.1.3.A of the Ontario Building Code specifies that the base daily design flow (Q) for a 3-bedroom residential occupancy is 1,600 Litres per day. Any additional fixtures or floor area may increase this baseline.
6Under OBC Table 8.2.1.3.A, what is the base daily design sanitary sewage flow (Q) for a 5-bedroom dwelling?
A.2,000 L/day
B.2,500 L/day
C.3,000 L/day
D.3,500 L/day
Explanation: According to Table 8.2.1.3.A, a 5-bedroom residential dwelling has a base daily design flow of 2,500 Litres per day.Dwellings with more than 5 bedrooms add 500 L/day for each additional bedroom.
7How is the daily design sewage flow calculated for a single-family dwelling that has 6 bedrooms under the OBC?
A.Take the 5-bedroom base of 2,500 L/day and add 300 L/day
B.Take the 5-bedroom base of 2,500 L/day and add 500 L/day
C.Multiply 6 bedrooms by 500 L/day to get 3,000 L/day
D.Take a flat rate of 3,500 L/day
Explanation: Table 8.2.1.3.A states that the base daily design flow for 5 bedrooms is 2,500 L/day, and we must add 500 L/day for each bedroom over 5. Thus, a 6-bedroom dwelling requires Q = 2,500 + 500 = 3,000 L/day.
8If a dwelling contains plumbing fixtures that total 24 fixture units, what is the additional daily sewage flow to be added under OBC Table 8.2.1.3.A?
A.50 L/day for each fixture unit over 20, resulting in 200 L/day
B.100 L/day for each fixture unit over 20, resulting in 400 L/day
C.50 L/day for each fixture unit over 15, resulting in 450 L/day
D.No addition is required unless fixture units exceed 30
Explanation: Table 8.2.1.3.A stipulates that we must add 50 L/day for each fixture unit over 20. Since the dwelling has 24 fixture units, the addition is (24 - 20) * 50 L/day = 200 L/day.
9Under the OBC, when calculating design flow Q, which finished area of a dwelling is excluded from the floor area calculations?
A.The kitchen and dining areas
B.The master bedroom suite
C.The finished basement
D.Any attached garage or workshop area
Explanation: OBC Table 8.2.1.3.A explicitly excludes the finished basement area when calculating the total finished area of a dwelling for design sewage flow additions.
10For a dwelling with a finished floor area (excluding basement) of 235 square meters, how is the additional daily flow calculated under Table 8.2.1.3.A?
A.Add 100 L/day for each 10 m² (or part thereof) over 200 m², resulting in 400 L/day
B.Add 50 L/day for each 10 m² (or part thereof) over 200 m², resulting in 200 L/day
C.Add 100 L/day for each 10 m² (or part thereof) over 150 m², resulting in 900 L/day
D.No additional flow is required as the floor area is under 300 square meters
Explanation: Table 8.2.1.3.A states that for dwellings with a finished area over 200 m² up to 400 m², we add 100 L/day for each 10 m² or part thereof over 200 m². The excess area is 235 - 200 = 35 m². This represents 4 increments of 10 m² (3 full and 1 partial), so 4 * 100 = 400 L/day must be added.

About the OBC On-site Sewage Systems Exam

The Ontario Building Code (OBC) On-site Sewage Systems examination is a qualification requirement for designers, installers, and municipal inspectors who design, construct, or inspect private sewage systems. The exam focuses on Part 8 of Division B of the 2024 Ontario Building Code, covering sewage classifications (Class 1 to 5), septic tank sizing, leaching bed designs (absorption trenches, shallow buried trenches, filter beds, dispersal beds), soil percolation (T-time) tests, loading rates, and mandatory clearance distances (setbacks) from property lines, wells, buildings, and water bodies.

Assessment

70 multiple-choice questions (Open book, 3 hours)

Time Limit

3 hours

Passing Score

70%

Exam Fee

$150.00 CAD (Humber Polytechnic / Ministry of Municipal Affairs and Housing)

OBC On-site Sewage Systems Exam Content Outline

20%

Sewage System Classifications & General Requirements

Classification of systems (Class 1 to 5), design flows, and general construction parameters under Section 8.1 and 8.2.

25%

Septic Tanks & Holding Tanks Sizing & Design

Calculations for working capacity, chamber partitions, and minimum volumes for residential and non-residential settings.

25%

Absorption Trenches & Leaching Bed Design

Sizing distribution piping length based on daily flow (Q) and soil percolation time (T), trench dimensions, and spacing.

15%

Soil Percolation, Mantles & Raised Systems

Soil T-time testing, loading rates, contact area, and mantle requirements for systems installed in imported fill.

15%

Filter Beds & Advanced Dispersal Beds

Design parameters, loading rates, and dimensional limits for filter beds, Type A and Type B dispersal beds.

How to Pass the OBC On-site Sewage Systems Exam

What You Need to Know

  • Passing score: 70%
  • Assessment: 70 multiple-choice questions (Open book, 3 hours)
  • Time limit: 3 hours
  • Exam fee: $150.00 CAD

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

OBC On-site Sewage Systems Study Tips from Top Performers

1Practice navigating the index of the OBC Compendium Volume 1 quickly, especially Part 8 (Sewage Systems) and Part 7 (Plumbing).
2Memorize key setbacks from Table 8.2.1.6.A and Table 8.2.1.6.B for septic tanks and leaching beds.
3Understand the difference between the base daily flow and the additional flow calculations (bedrooms vs. floor area vs. fixture units).
4Be comfortable performing formulas: L = (Q * T) / 200 for trenches, and A = (Q * T) / 850 for raised bed contact areas.
5Pay attention to the wording of questions: verify if a system is residential or non-residential, as septic tank capacity sizing rules differ (2Q vs 3Q).

Frequently Asked Questions

Is the OBC On-site Sewage Systems exam open book?

Yes, you are permitted to use a hard copy of the 2024 Building Code Compendium. You can highlight and tab the document, but writing notes in the margins is restricted.

What is the passing score and format?

The exam consists of 70 multiple-choice questions. You have 3 hours to complete it, and you must achieve a passing score of at least 70%.

How is daily design flow (Q) determined for residential houses?

Under Article 8.2.1.3., daily flow is based on the number of bedrooms, with additional volumes added for finished area exceeding 200 square meters or fixture units exceeding 20. The calculation yielding the highest flow is used.

Can I take the exam online?

Yes, Humber Polytechnic offers online proctored examinations. You must have a stable internet connection, a webcam, and meet system requirements.