PracticeVideosBlogFlashcardsEspañol
All Practice Exams

100+ Free OBC Plumbing All Buildings Practice Questions

Pass your Ontario Building Code Exam: Plumbing - All Buildings exam on the first try — instant access, no signup required.

✓ No registration✓ No credit card✓ No hidden fees✓ Start practicing immediately
N/A Pass Rate
100+ Questions
100% Free

Loading practice questions...

Same family resources

Explore More Ontario Building Code (OBC) Certifications

Continue into nearby exams from the same family. Each card keeps practice questions, study guides, flashcards, videos, and articles in one place.

Ontario Building Code Exam: Building Services

Practice Questions

Ontario Building Code Exam: Building Structural

Practice Questions

Ontario Building Code Exam: Complex Buildings

Practice Questions

Ontario Building Code Exam: Designer Legal/Process

Practice Questions

Ontario Building Code Exam: Detection, Lighting and Power

Practice Questions

Ontario Building Code Exam: Fire Protection

Practice Questions
2026 Statistics

Key Facts: OBC Plumbing All Buildings Exam

70

Total Questions

Humber OBC Exam Guidelines

70%

Passing Score

MMAH Syllabus

3 Hours

Time Limit

Humber OBC Exam Guidelines

$150.00

Fee (CAD)

Humber OBC Exam Guidelines

Part 7

OBC Scope

OBC Compendium

The OBC Plumbing - All Buildings exam consists of 70 multiple-choice questions with a 3-hour time limit. It is an open-book exam based on the 2024 Ontario Building Code, requiring a 70% score to pass.

Sample OBC Plumbing All Buildings Practice Questions

Try these sample questions to test your OBC Plumbing All Buildings exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Under the 2024 Ontario Building Code, what is the minimum downward slope required for a horizontal sanitary drainage pipe with a nominal size of NPS 3 or less?
A.1 in 25 (4%)
B.1 in 100 (1%)
C.1 in 200 (0.5%)
D.1 in 50 (2%)
Explanation: According to Division B, Article 7.4.8.1. of the 2024 Ontario Building Code, the minimum downward slope for horizontal drainage piping of NPS 3 or less is 1 in 50 (2%). This slope ensures adequate velocity is maintained to prevent the accumulation of solids and clogging.
2What is the minimum downward slope required for a horizontal sanitary drainage pipe with a nominal size of NPS 4 or larger under the 2024 OBC?
A.1 in 25 (4%)
B.1 in 200 (0.5%)
C.1 in 100 (1%)
D.1 in 50 (2%)
Explanation: According to Division B, Article 7.4.8.1. of the 2024 OBC, horizontal drainage piping of NPS 4 or larger is permitted a minimum downward slope of 1 in 100 (1%). This is because larger pipes can maintain scouring velocity with less slope.
3What is the maximum spacing between cleanouts on a horizontal sanitary drainage pipe smaller than NPS 3, when using two-way rodding?
A.30 metres
B.10 metres
C.7.5 metres
D.15 metres
Explanation: Division B, Table 7.4.7.2. of the 2024 OBC specifies that the maximum spacing between cleanouts on a horizontal drainage pipe smaller than NPS 3 is 15 metres for two-way rodding (7.5 metres for one-way rodding).
4What is the maximum spacing between cleanouts on a horizontal sanitary drainage pipe of NPS 3 or 4, when using two-way rodding, under the 2024 OBC?
A.15 metres
B.45 metres
C.30 metres
D.20 metres
Explanation: According to Division B, Table 7.4.7.2. of the 2024 OBC, the maximum distance between cleanouts on horizontal drainage piping of NPS 3 or 4 is 30 metres for two-way rodding (15 metres for one-way rodding).
5What is the minimum size of a cleanout serving a nominal NPS 3 drainage pipe?
A.NPS 2
B.NPS 4
C.NPS 1-1/2
D.NPS 3
Explanation: Under Division B, Article 7.4.7.2. of the 2024 OBC, for drainage piping of NPS 4 or smaller, the cleanout must be of the same nominal size as the pipe it serves. Therefore, a cleanout serving an NPS 3 pipe must be at least NPS 3.
6Under the 2024 OBC, what is the minimum permitted size of a cleanout serving an NPS 6 horizontal drainage pipe?
A.NPS 6
B.NPS 5
C.NPS 3
D.NPS 4
Explanation: According to Division B, Article 7.4.7.2. of the OBC, for drainage piping larger than NPS 4, the cleanout opening is not required to be larger than NPS 4. Therefore, for an NPS 6 pipe, the minimum cleanout size is NPS 4.
7Where is a grease interceptor mandatory under the 2024 Ontario Building Code?
A.Dental office clinics
B.Residential kitchen sinks
C.Commercial food preparation areas
D.Chemical laboratories
Explanation: Division B, Article 7.4.4.3. of the 2024 OBC requires that grease interceptors be installed in food preparation and processing areas of commercial, institutional, and public establishments to prevent grease from blocking the public sewer system.
8What is the minimum nominal trap size for a residential kitchen sink under the 2024 OBC?
A.NPS 1-1/4
B.NPS 3
C.NPS 1-1/2
D.NPS 2
Explanation: According to Division B, Table 7.4.9.3. of the 2024 OBC, the minimum nominal trap size for a domestic kitchen sink (single or double compartment) is NPS 1-1/2 (38 mm). This size provides adequate drainage capacity for residential kitchen usage.
9What is the minimum nominal trap size for a residential lavatory (wash basin) under the 2024 OBC?
A.NPS 1-1/4
B.NPS 2
C.NPS 1-1/2
D.NPS 1
Explanation: Under Division B, Table 7.4.9.3. of the 2024 OBC, the minimum nominal trap size for a bathroom lavatory (wash basin) is NPS 1-1/4 (32 mm). This is the smallest standard trap size permitted for any fixture.
10What is the minimum nominal water service pipe size for a single-family dwelling under the 2024 OBC?
A.NPS 1
B.NPS 1-1/4
C.NPS 3/4
D.NPS 1/2
Explanation: According to Division B, Article 7.6.3.1. of the 2024 OBC, the minimum size of a water service pipe supplying a single-family dwelling is NPS 3/4 (19 mm). This size ensures adequate volume and pressure are delivered to the building.

About the OBC Plumbing All Buildings Exam

The Ontario Building Code (OBC) Plumbing - All Buildings Qualification Examination is administered by Humber Polytechnic on behalf of the Ministry of Municipal Affairs and Housing. This exam validates the candidate's knowledge of Division B, Part 7 (Plumbing Systems) of the 2024 Ontario Building Code, covering all classes of occupancies. Key subjects include water service and distribution system design, sanitary and storm drainage design, venting configurations, backflow prevention, and testing protocols. This qualification is required for plumbing inspectors, plans examiners, and designers seeking BCIN certification in Ontario.

Assessment

70 multiple-choice questions (Open-book, computer-based)

Time Limit

3 hours

Passing Score

70%

Exam Fee

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

OBC Plumbing All Buildings Exam Content Outline

35%

Drainage Systems

Covers sizing and design of sanitary and storm drainage systems, slope, cleanouts, interceptors, and traps under Section 7.4.

30%

Venting Systems

Covers wet venting, circuit venting, stack venting, relief vents, yoke vents, and terminal height rules under Section 7.5.

25%

Water Distribution Systems

Covers sizing, materials, backflow prevention, cross-connection control, and system pressure limits under Section 7.6.

10%

Materials, Joints, and Testing

Covers hanger supports, jointing methods, material standards, and testing procedures (water, air, and ball tests).

How to Pass the OBC Plumbing All Buildings Exam

What You Need to Know

  • Passing score: 70%
  • Assessment: 70 multiple-choice questions (Open-book, computer-based)
  • 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 Plumbing All Buildings Study Tips from Top Performers

1Familiarize yourself with Table 7.4.9.3 (fixture drainage units) and Table 7.6.3.2.A (water supply fixture units). Keep these pages tabbed in your physical copy.
2Practice navigating between Section 7.4 (Drainage) and Section 7.5 (Venting), as sizing vents requires knowing the drainage load draining through them.
3Understand the key differences between wet venting and circuit venting, and their layout limits.
4Review the testing requirements in Section 7.7: air tests (35 kPa) vs water tests (3 m water column) on drainage systems.
5Manage your time carefully: with 70 questions in 3 hours, you have an average of 2.6 minutes per question. Fast code search is essential.

Frequently Asked Questions

Is the OBC Plumbing - All Buildings exam open book?

Yes. Candidates are permitted to bring physical copies of the 2024 Ontario Building Code Compendium (Volumes 1 and 2) or approved PDF copies into the testing environment.

What is the passing score for the OBC Plumbing - All Buildings exam?

The passing threshold is 70%. Candidates must answer at least 49 of the 70 questions correctly within the 3-hour limit.

Who needs to take this examination?

Plumbing inspectors, municipal plans examiners, and plumbing designers seeking a Building Code Identification Number (BCIN) to design or inspect systems for buildings other than houses must pass this exam.

Are calculators allowed during the exam?

Yes. Candidates are allowed to use basic, non-programmable calculators to perform sizing and loading calculations.