Journeyman Plumbers Drainage, Waste, and Vent Systems Questions and Answers — Questions and Answers
Question 1: According to most plumbing codes, what is the required range for a fixture trap's liquid seal depth?
- 1 inch to 3 inches
- 2 inches to 4 inches (Correct answer)
- 3 inches to 5 inches
- 4 inches to 6 inches
Correct answer: 2 inches to 4 inches
A trap seal between 2 and 4 inches is required to effectively block sewer gases while preventing siphonage or sluggish flow. A seal less than 2 inches is prone to evaporation or being siphoned out, and a seal deeper than 4 inches can slow drainage and lead to blockages.
Question 2: A plumber is installing the drain for a kitchen sink, which has a 1-1/2 inch P-trap. What is the maximum horizontal distance the trap arm can be from the vent fitting?
- 5 feet
- 6 feet
- 3 feet 6 inches (Correct answer)
- 8 feet
Correct answer: 3 feet 6 inches
The maximum horizontal distance between a fixture trap and its vent is determined by the size of the trap arm. For a 1-1/2 inch pipe, this distance is typically limited to 3 feet 6 inches to ensure proper venting and prevent the trap from being siphoned.
Question 3: Which of the following is the primary purpose of a vent in a drainage system?
- To provide a means of cleaning the drain line
- To equalize pressure and protect trap seals (Correct answer)
- To increase the velocity of the wastewater
- To filter out solid waste materials
Correct answer: To equalize pressure and protect trap seals
The primary function of a vent system is to introduce air into the drainage pipes. This equalizes the atmospheric pressure within the system, preventing the siphoning of trap seals and allowing wastewater to flow freely by gravity.
Question 4: A journeyman plumber is planning a horizontal DWV (Drainage, Waste, and Vent) line using 4-inch diameter pipe. What is the minimum required slope for this pipe?
- 1/16 inch per foot
- 1/2 inch per foot
- 1/4 inch per foot
- 1/8 inch per foot (Correct answer)
Correct answer: 1/8 inch per foot
For horizontal drainage pipes 3 inches in diameter or larger, a minimum slope of 1/8 inch per foot is generally permitted. Pipes smaller than 3 inches typically require a minimum slope of 1/4 inch per foot to ensure proper flow and scouring action.
Question 5: When installing a wet vent for a bathroom group (e.g., toilet, lavatory, and bathtub), which of the following is a critical requirement according to most plumbing codes?
- The wet-vented section must be two pipe sizes larger than the largest fixture drain.
- Only fixtures on different floor levels can be connected to the wet vent.
- The toilet must always be the most upstream fixture connected to the wet vent.
- All fixtures served by the wet vent must be on the same floor level. (Correct answer)
Correct answer: All fixtures served by the wet vent must be on the same floor level.
A key principle of wet venting is that all the interconnected fixtures sharing the vent must be located on the same story or floor level. This ensures the proper hydraulic and pneumatic conditions for the drain to also function as a vent.
Question 6: Cleanouts are required in a drainage system to allow for access. For a horizontal drainage pipe that is 100 feet long, where must cleanouts be located?
- At the upper terminal and for each 50 feet of developed length.
- Only at the upper terminal end of the pipe.
- At the upper terminal and for each 100 feet, or fraction thereof, of developed length. (Correct answer)
- Only at changes of direction greater than 90 degrees.
Correct answer: At the upper terminal and for each 100 feet, or fraction thereof, of developed length.
Plumbing codes require a cleanout at the upper terminal of each horizontal drain and for each 100 feet of developed length or fraction thereof. This ensures that the entire length of the pipe is accessible for cleaning and maintenance.
Journeyman Plumbers Drainage, Waste, and Vent Systems Questions and Answers
According to most plumbing codes, what is the required range for a fixture trap's liquid seal depth?