Master Plumber Exam Drainage, Waste, and Venting 5 — Questions and Answers
Question 1: Under the IPC, what is the maximum developed length of a 1.5-inch trap arm (from trap weir to vent)?
- 3.5 feet (Correct answer)
- 5 feet
- 6 feet
- 8 feet
Correct answer: 3.5 feet
The IPC limits the trap arm of a 1.5-inch pipe to a maximum developed length of 3.5 feet from the trap weir to the vent.
Question 2: When two fixtures are on opposite sides of a wall and share a common vertical drain, the configuration is called a:
- Back-to-back venting arrangement
- Double sanitary tee installation
- Wet-vented stack
- Common vent arrangement (Correct answer)
Correct answer: Common vent arrangement
A common vent arrangement allows two fixtures at the same floor level on opposite sides of a partition to share a single vent pipe.
Question 3: Which of the following is an example of a self-siphoning trap condition?
- A floor drain trap evaporating due to infrequent use
- A lavatory trap losing its seal during the fixture's own rapid drainage (Correct answer)
- A toilet trap losing seal due to water hammer
- A laundry tub losing seal when the washing machine discharges
Correct answer: A lavatory trap losing its seal during the fixture's own rapid drainage
Self-siphonage occurs when a fixture's own rapid discharge creates enough negative pressure to pull the water seal from its own trap.
Question 4: What is the minimum vent pipe diameter for a single water closet?
- 1 inch
- 1.5 inches
- 2 inches (Correct answer)
- 3 inches
Correct answer: 2 inches
The IPC requires a minimum 2-inch vent for a water closet because of the high volume of waste and the 4-inch drain size associated with water closets.
Question 5: A sewage ejector system is required when a fixture drain is located:
- More than 20 feet from the main stack
- Below the upstream manhole cover elevation of the public sewer (Correct answer)
- In a room without natural ventilation
- On a floor above the building drain level
Correct answer: Below the upstream manhole cover elevation of the public sewer
A sewage ejector is required when fixtures are below the upstream manhole cover elevation of the public sewer so that waste can be pumped up to the gravity sewer.
Question 6: What is the maximum unvented length (developed length) of a drain pipe serving a 3-inch trap arm under the IPC?
- 4 feet
- 5 feet
- 6 feet (Correct answer)
- 8 feet
Correct answer: 6 feet
The IPC allows a maximum trap arm developed length of 6 feet for a 3-inch diameter trap arm from the trap weir to the vent.
Question 7: Under the IPC, where must the cleanout at the base of a soil stack be located?
- At the point where the stack enters the footing
- Within 10 feet of the base of the stack in the horizontal drain (Correct answer)
- Immediately above the lowest branch connection
- At the point where the stack connects to the building drain
Correct answer: Within 10 feet of the base of the stack in the horizontal drain
The IPC requires a cleanout within 10 feet of the base of each soil and waste stack in the horizontal drain to allow rodding of the stack from the bottom.
Master Plumber Exam Drainage, Waste, and Venting 5
Under the IPC, what is the maximum developed length of a 1.5-inch trap arm (from trap weir to vent)?