Journeyman Plumbers Exam Isometric Analysis and Math 3 — Questions and Answers
Question 1: What is the approximate center-to-center measurement when two 1.5-inch 90-degree elbows are connected with a nipple and the take-out of each elbow is 1.125 inches?
- The sum of the two take-outs subtracted from the overall face-to-face dimension (Correct answer)
- The length of the nipple only
- The overall face-to-face dimension only
- Twice the take-out added to the nipple length
Correct answer: The sum of the two take-outs subtracted from the overall face-to-face dimension
Center-to-center = face-to-face overall dimension minus both elbow take-outs.
Question 2: When drawing a 3D pipe system in isometric view, pipes going into and out of the page (north-south) are drawn along which axis?
- The left-leaning 30-degree axis (Correct answer)
- The right-leaning 30-degree axis
- The vertical axis
- At true horizontal
Correct answer: The left-leaning 30-degree axis
The left-leaning 30-degree axis on an isometric drawing represents the north-south (depth) direction.
Question 3: A rolling offset requires calculating both the horizontal offset and the vertical rise. If the horizontal set is 9 inches and the vertical rise is 12 inches, what is the diagonal set?
- 15 inches (Correct answer)
- 21 inches
- 10.5 inches
- 13 inches
Correct answer: 15 inches
Diagonal set = √(9² + 12²) = √(81 + 144) = √225 = 15 inches using the Pythagorean theorem.
Question 4: If a 4-inch drain pipe must maintain 1/8-inch-per-foot slope over 24 feet, what is the elevation change from inlet to outlet?
- 3 inches (Correct answer)
- 6 inches
- 2 inches
- 4 inches
Correct answer: 3 inches
Total drop = 24 feet × 0.125 inches/foot = 3 inches.
Question 5: What fitting constant (take-out) is used when calculating the cut length of pipe for a standard 90-degree elbow?
- The take-out varies by pipe size and elbow type (Correct answer)
- Always 1 inch regardless of pipe size
- Always 2 inches regardless of pipe size
- Always equal to the pipe diameter
Correct answer: The take-out varies by pipe size and elbow type
Take-out (fitting allowance) varies by pipe diameter and elbow type and must be looked up in a fittings table.
Question 6: In an isometric sketch of a plumbing system, what does a dashed line typically indicate?
- A pipe hidden behind another element or run underground/in a wall (Correct answer)
- A future pipe not yet installed
- A pipe running at 45 degrees
- A flexible connector
Correct answer: A pipe hidden behind another element or run underground/in a wall
Dashed lines on isometric drawings represent pipes that are hidden from view or run underground/in walls.
Question 7: A 22.5-degree offset has a travel constant of approximately 2.613. If the set is 5 inches, what is the travel?
- 13.07 inches (Correct answer)
- 10.00 inches
- 7.50 inches
- 5.00 inches
Correct answer: 13.07 inches
Travel = set × travel constant = 5 × 2.613 = 13.07 inches.
Journeyman Plumbers Exam Isometric Analysis and Math 3
What is the approximate center-to-center measurement when two 1.5-inch 90-degree elbows are connected with a nipple and the take-out of each elbow is 1.125 inches?