Free Journeyman Plumbers Drain, Waste, Vent Systems Questions and Answers — Questions and Answers
Question 1: According to most plumbing codes, what is the maximum allowable distance between cleanouts on a 4-inch horizontal drainage line?
- 50 feet
- 75 feet
- 100 feet (Correct answer)
- 150 feet
Correct answer: 100 feet
Both the International Plumbing Code (IPC) and the Uniform Plumbing Code (UPC) generally require cleanouts on horizontal drains to be installed at intervals not exceeding 100 feet. Some local codes might have slight variations, but 100 feet is the most common standard.
Question 2: A plumber is installing a wet vent for a single bathroom group. Which of the following is a universal requirement for this type of installation?
- The wet-vented section must be two pipe sizes larger than the minimum required drain size.
- The toilet must be the last fixture connected to the horizontal wet vent.
- All fixtures served by the wet vent must be on the same floor level. (Correct answer)
- A maximum of four fixtures can be served by the wet vent.
Correct answer: All fixtures served by the wet vent must be on the same floor level.
A key rule for both horizontal and vertical wet venting, according to major plumbing codes, is that all the fixtures connecting to the wet vent must be located on the same story or floor level. While other rules apply regarding pipe sizing and fixture order, the same-floor requirement is fundamental.
Question 3: What is the minimum required clearance in front of a cleanout for a 3-inch drain pipe to allow for proper rodding and servicing?
- 12 inches
- 18 inches (Correct answer)
- 24 inches
- 36 inches
Correct answer: 18 inches
The International Plumbing Code (IPC) specifies that cleanouts on 6-inch and smaller pipes must have a clearance of not less than 18 inches for rodding. The Uniform Plumbing Code (UPC) has similar requirements, stating that pipes over 2 inches need at least 24 inches, but 18 inches is a widely accepted minimum for smaller pipes.
Question 4: A residential bathroom group consists of a standard water closet (1.6 GPF), a lavatory, and a bathtub. What is the total Drainage Fixture Unit (DFU) load for this group that should be used for sizing the branch drain?
- 5 DFU
- 6 DFU (Correct answer)
- 7 DFU
- 8 DFU
Correct answer: 6 DFU
Individually, a 1.6 GPF water closet is typically 4 DFU, a lavatory is 1 DFU, and a bathtub is 2 DFU, totaling 7 DFU. However, plumbing codes recognize that not all fixtures are used simultaneously. Therefore, when calculating the load for a bathroom group on a branch, a lower value is often assigned. Adding them up: Lavatory (1 DFU) + Bathtub (2 DFU) + Water Closet (3-4 DFU) would be 6-7 DFU. Different codes may vary slightly, but 6 DFU is a common value. For example, some codes value a 1.6 GPF toilet at 3 DFU, making the total 6.
Question 5: Which of the following describes the minimum required length for a trap arm, as measured from the trap weir to the inner edge of the vent?
- It must be equal to the diameter of the trap arm.
- It must be at least 12 inches long.
- It must be at least two times the diameter of the trap arm. (Correct answer)
- It must not exceed the diameter of the trap arm.
Correct answer: It must be at least two times the diameter of the trap arm.
To prevent crown-venting, where the vent opening becomes fouled by waste, and to ensure proper function, the trap arm must have a minimum length. The code specifies this minimum length to be no less than two times the nominal pipe diameter of the trap arm itself.
Question 6: A plumber needs to connect a horizontal branch drain to a vertical stack. To ensure proper flow and prevent blockages, which type of fitting is most appropriate for this connection?
- A sanitary tee
- A vent tee
- A short sweep 90-degree elbow
- A combination wye and 1/8 bend or a long sweep fitting (Correct answer)
Correct answer: A combination wye and 1/8 bend or a long sweep fitting
When transitioning from a horizontal drain to a vertical stack, it is critical to use fittings that promote a smooth, sweeping change in direction. A combination wye and 1/8 bend (or a long sweep fitting) is required to prevent solids from building up at the change of direction, which can occur with the sharper turn of a sanitary tee. Sanitary tees are typically used for vertical to horizontal transitions.
Free Journeyman Plumbers Drain, Waste, Vent Systems Questions and Answers
According to most plumbing codes, what is the maximum allowable distance between cleanouts on a 4-inch horizontal drainage line?