100+ Free OBC Plumbing House Practice Questions

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Sample OBC Plumbing House Practice Questions

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1According to Ontario Building Code (OBC) Division B, Part 7, what is the minimum required water seal depth for a standard fixture trap?

A.25 mm

B.38 mm

C.50 mm

D.75 mm

Explanation: OBC Division B, Sentence 7.2.3.1.(1) states that the water seal of a fixture trap shall be not less than 38 mm (1.5 inches). This depth is designed to prevent sewer gases from entering the building while maintaining a self-cleansing action.

2Under the OBC, above what temperature must sewage or waste water be cooled before it is discharged into a sanitary drainage system?

A.50°C

B.65°C

C.75°C

D.90°C

Explanation: OBC Division B, Article 7.4.4.2 requires that where a fixture discharges sewage or clear-water waste at a temperature above 65°C, provision must be made to cool the waste to 65°C or less before it enters a sanitary drainage system. (Clear-water waste discharged to a storm drainage system must be cooled to 40°C or less.) This protects plastic piping and joints from heat damage.

3Under what condition is Type M copper tubing permitted for use in residential water systems under the OBC?

A.Only for underground water service lines

B.Only for above-ground water distribution systems inside a building

C.For both underground service and above-ground distribution

D.It is not permitted for potable water systems under any condition

Explanation: OBC Division B, Sentence 7.2.7.4.(2) permits Type M copper tubing to be used for water distribution systems above ground inside a building. It is too thin for underground or slab installations.

4Which of the following standards must ABS plastic pipe and fittings comply with for drainage and venting applications in Ontario?

A.CAN/CSA-B137.5

B.CAN/CSA-B181.1

C.CAN/CSA-B181.2

D.ASTM D2564

Explanation: OBC Division B, Table 7.2.5.10. specifies that ABS plastic pipe and fittings must comply with CAN/CSA-B181.1 standard.

5Under the OBC, solder and fluxes used to join copper pipe in a potable water system must contain no more than what percentage of lead?

A.0.2%

B.0.5%

C.1.0%

D.2.0%

Explanation: OBC Division B, Sentence 7.2.9.1.(1) requires that solders and fluxes containing more than 0.2% lead shall not be used in water systems conveying potable water.

6What is the minimum permitted size of a floor drain installed in a residential basement under the OBC?

A.1-1/2 inches (38 mm)

B.2 inches (50 mm)

C.3 inches (75 mm)

D.4 inches (100 mm)

Explanation: OBC Division B, Sentence 7.2.2.4.(1) states that where a floor drain is installed in a basement, the minimum size of the floor drain outlet and drain pipe shall be 3 inches (75 mm).

7When sheet lead is used for roof flashing around vent terminals in residential construction, what is the minimum required thickness?

A.0.85 mm

B.1.20 mm

C.1.73 mm

D.2.50 mm

Explanation: OBC Division B, Table 7.2.11.2. specifies that sheet lead for roof flashing at vent terminals must be at least 1.73 mm thick (equivalent to 4 lb/sq ft).

8Which of the following fixture traps is exempt from the requirement of having a cleanout plug at the bottom of the trap under the OBC?

A.A laundry tub trap

B.A kitchen sink trap

C.A water closet trap

D.A bathtub trap

Explanation: OBC Division B, Sentence 7.2.3.1.(2) states that fixture traps do not require a cleanout if the trap is integral with the fixture (such as a water closet) or if the fixture is easily removable.

9What is the maximum horizontal spacing permitted for supports of ABS drainage piping in a house?

A.1.0 m

B.1.2 m

C.1.5 m

D.2.0 m

Explanation: OBC Division B, Table 7.3.4.5. states that horizontal ABS drainage piping must be supported at intervals not exceeding 1.2 m to prevent sagging and ensure proper slope.

10Where are slip joints permitted to be used in the drainage piping system of a house under the OBC?

A.Anywhere in the horizontal drainage system

B.Only on the inlet side of a trap or in the trap seal

C.In vertical waste stacks only

D.Slip joints are completely prohibited in residential drainage systems

Explanation: OBC Division B, Sentence 7.2.10.6.(1) specifies that slip joints may be used only on the inlet side of a trap or in the trap seal. They are not allowed on the sewer side of the trap due to the risk of sewer gas leaks.

About the OBC Plumbing House Exam

This practice exam covers materials, potable water systems, drainage, waste, venting, inspections, and testing requirements for houses under the Ontario Building Code.

Assessment

100 multiple-choice questions

Time Limit

3 hours

Passing Score

60%

Exam Fee

Free (Ontario Ministry of Municipal Affairs and Housing)

OBC Plumbing House Exam Content Outline

20%

Materials & Equipment

Specification of piping materials, joints, fixtures, and backflow preventers.

20%

Potable Water Systems

Design and sizing of water distribution systems, pressure control, and water service pipes.

20%

Drainage & Waste Systems

Sizing and installation of sanitary drainage, building sewers, cleanouts, and interceptors.

20%

Venting Systems

Sizing and routing of stack vents, vent stacks, wet venting, and dual venting.

20%

Inspection, Testing & Permits

OBC administrative rules, permit requirements, testing procedures, and site inspections.

How to Pass the OBC Plumbing House Exam

What You Need to Know

Passing score: 60%
Assessment: 100 multiple-choice questions
Time limit: 3 hours
Exam fee: Free

Keys to Passing

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

Frequently Asked Questions

What is the format of the OBC Plumbing House exam?

The exam consists of 100 multiple-choice questions covering all five content domains.

What is the passing score for the OBC Plumbing House exam?

Candidates must score at least 60% to pass the exam.