Free Journeyman Plumbers Isometric Drawings and Math Questions and Answers — Questions and Answers
Question 1: A plumber needs to create a 45-degree offset in a horizontal pipe run. If the distance between the centerlines of the two parallel pipes (the offset) is 20 inches, what is the center-to-center length of the travel piece?
- 20 inches
- 40 inches
- 28.28 inches (Correct answer)
- 14.14 inches
Correct answer: 28.28 inches
For a 45-degree offset, the travel length is calculated by multiplying the offset distance by the constant 1.414. Therefore, 20 inches * 1.414 = 28.28 inches.
Question 2: A horizontal drainage pipe that is 48 feet long must be installed with a uniform grade of 1/4 inch per foot. What is the total fall of the pipe from its highest point to its lowest point?
- 6 inches
- 12 inches (Correct answer)
- 24 inches
- 8 inches
Correct answer: 12 inches
The total fall is calculated by multiplying the length of the pipe in feet by the required grade in inches per foot. Calculation: 48 feet * (1/4 inch/foot) = 12 inches.
Question 3: In an isometric plumbing drawing, a pipe is shown as a vertical line. It then turns and runs horizontally away from the viewer and to the right. Which of the following best describes how the horizontal pipe would be drawn?
- As a horizontal line running straight to the right.
- As a vertical line running down.
- As a line angled at 30 degrees up from the horizontal. (Correct answer)
- As a line angled at 45 degrees up from the horizontal.
Correct answer: As a line angled at 30 degrees up from the horizontal.
In standard isometric drawings, vertical lines are drawn vertically, while horizontal lines (representing length and width) are drawn at 30 degrees to the horizontal plane to create a three-dimensional view on a two-dimensional surface.
Question 4: A plumber has a travel piece that is 35 inches long and was installed using two 45-degree fittings. What is the offset distance between the centerlines of the two parallel pipes?
- 49.5 inches
- 35 inches
- 17.5 inches
- 24.75 inches (Correct answer)
Correct answer: 24.75 inches
To find the offset when the travel length is known, you multiply the travel by 0.707 (the reciprocal of 1.414) or divide the travel by 1.414. Calculation: 35 inches * 0.707 = 24.745 inches, which rounds to 24.75 inches.
Question 5: When creating an offset using two 60-degree fittings, the distance between the centerlines of the parallel pipes is 15 inches. What is the approximate length of the travel pipe required between the fittings?
- 30.0 inches
- 17.3 inches (Correct answer)
- 21.2 inches
- 15.0 inches
Correct answer: 17.3 inches
The constant for a 60-degree offset is 1.155. The travel is calculated by multiplying the offset (15 inches) by 1.155, which equals 17.325 inches.
Question 6: An isometric drawing shows a horizontal pipe run that must clear an obstruction by using a vertical offset. If the developed length (travel) of the pipe between the two 45-degree fittings is 50 inches, what is the vertical height (offset) gained?
- 70.7 inches
- 50 inches
- 35.35 inches (Correct answer)
- 25 inches
Correct answer: 35.35 inches
To find the offset (vertical height) from a known travel length in a 45-degree offset, divide the travel length by the constant 1.414 or multiply by 0.707. Calculation: 50 inches / 1.414 = 35.36 inches.
Free Journeyman Plumbers Isometric Drawings and Math Questions and Answers
A plumber needs to create a 45-degree offset in a horizontal pipe run.
If the distance between the centerlines of the two parallel pipes (the offset) is 20 inches, what is the center-to-center length of the travel piece?