Master Plumber Exam DWV and Storm Drainage 5 — Questions and Answers
Question 1: What is the maximum trap-to-vent distance for a 3-inch trap arm under the IPC?
- 4 feet
- 5 feet
- 6 feet
- 10 feet (Correct answer)
Correct answer: 10 feet
Per IPC Table 909.1, a 3-inch trap arm may extend a maximum of 10 feet from the trap to the vent.
Question 2: In a DWV system, which stack is used exclusively for venting and carries no waste?
- Soil stack
- Waste stack
- Vent stack (Correct answer)
- Circuit vent
Correct answer: Vent stack
A vent stack is a vertical pipe used solely for venting purposes; it carries no sewage or waste water.
Question 3: When is an 'island fixture vent' (Chicago loop) used?
- When a fixture is located on an exterior wall
- When a fixture cannot be vented through the roof due to its location in a kitchen island (Correct answer)
- When a stack vent is over 50 feet tall
- When two fixtures share a common P-trap
Correct answer: When a fixture cannot be vented through the roof due to its location in a kitchen island
An island fixture vent loops up from the drain and back down, then runs beneath the floor to connect to a vent stack, used when fixtures are in islands away from walls.
Question 4: What is the minimum depth of cover required for a building sewer installed under a driveway?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
The IPC requires a minimum of 18 inches of cover for a building sewer installed under a driveway subject to vehicular traffic.
Question 5: A 'circuit vent' in a DWV system serves which purpose?
- It vents a single fixture individually
- It vents a battery of fixtures connected to a horizontal branch with a single vent at the end (Correct answer)
- It replaces all individual fixture vents in a building
- It connects the soil stack directly to the vent stack
Correct answer: It vents a battery of fixtures connected to a horizontal branch with a single vent at the end
A circuit vent serves a group (battery) of fixtures on a common horizontal branch by venting the branch with a single vent connection at its upstream end.
Question 6: Which of the following describes a 'flat' or 'grade' issue in horizontal drain piping?
- Pipe installed at less than the minimum required slope, causing solids to settle (Correct answer)
- Pipe installed at too steep a slope, causing liquid to outrun solids
- A drain installed above the flood level rim of a fixture
- A vent pipe installed horizontally without proper slope
Correct answer: Pipe installed at less than the minimum required slope, causing solids to settle
A flat or insufficient grade means the pipe has less than the minimum slope, causing flow velocity to drop below self-scouring speed and allowing solids to settle and block the pipe.
Question 7: What is the rational method formula (Q = CIA) used for in storm drainage?
- Calculating pipe wall thickness under hydraulic pressure
- Estimating peak storm water runoff from a drainage area (Correct answer)
- Determining the required number of roof drains
- Sizing the grease interceptor capacity
Correct answer: Estimating peak storm water runoff from a drainage area
The rational method (Q = CIA) is used to estimate peak runoff where Q is flow, C is the runoff coefficient, I is rainfall intensity, and A is drainage area.
Master Plumber Exam DWV and Storm Drainage 5
What is the maximum trap-to-vent distance for a 3-inch trap arm under the IPC?