Isometric Analysis and Math Flashcards
7 cards from real Journeyman Plumbers Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Isometric Analysis and Math flashcards as text
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?
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.
When drawing a 3D pipe system in isometric view, pipes going into and out of the page (north-south) are drawn along which axis?
Answer: The left-leaning 30-degree axis
The left-leaning 30-degree axis on an isometric drawing represents the north-south (depth) direction.
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?
Answer: 15 inches
Diagonal set = √(9² + 12²) = √(81 + 144) = √225 = 15 inches using the Pythagorean theorem.
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?
Answer: 3 inches
Total drop = 24 feet × 0.125 inches/foot = 3 inches.
What fitting constant (take-out) is used when calculating the cut length of pipe for a standard 90-degree elbow?
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.
In an isometric sketch of a plumbing system, what does a dashed line typically indicate?
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.
A 22.5-degree offset has a travel constant of approximately 2.613. If the set is 5 inches, what is the travel?
Answer: 13.07 inches
Travel = set × travel constant = 5 × 2.613 = 13.07 inches.