Journeyman Plumbers Isometric Analysis and Math Questions and Answers

Question 1

A plumber needs to install a 45-degree offset. The horizontal distance between the centerlines of the two parallel pipes, known as the 'set', is 20 inches. What is the center-to-center length of the 'travel' piece of pipe?

Accepted Answer

28 1/4 inches

Answer

To find the travel for a 45-degree offset, you multiply the 'set' by the constant 1.414. In this case, 20 inches (set) x 1.414 = 28.28 inches. The closest fractional answer is 28 1/4 inches (28.25).

Question 2

A horizontal drainage line that is 48 feet long must be installed with a uniform grade of 1/8 inch per foot. What is the total fall of the pipe from its starting point to its end point?

Accepted Answer

6 inches

Answer

To calculate the total fall, multiply the length of the pipe run by the required grade per foot. Calculation: 48 feet * (1/8 inch/foot) = 6 inches.

Question 3

When fabricating a rolling offset, a pipe must shift 15 inches horizontally (run) and 20 inches vertically (rise). What is the 'true offset' of this configuration?

Accepted Answer

25 inches

Answer

The true offset of a rolling offset is the hypotenuse of the right triangle formed by the run and the rise. Using the Pythagorean theorem (a² + b² = c²), the calculation is 15² + 20² = c². This becomes 225 + 400 = 625. The square root of 625 is 25. Therefore, the true offset is 25 inches.

Question 4

In pipe measurement, the dimension that must be subtracted from a center-to-center measurement to determine the exact cut length of the pipe is known as:

Accepted Answer

Fitting allowance

Answer

The fitting allowance, or take-off, is the length from the center of a fitting to the face of the fitting's socket or hub. This amount is subtracted from the center-to-center measurement for each fitting used to find the precise cut length of the pipe.

Question 5

Which of the following is the correct mathematical constant used to calculate the 'travel' piece when the 'set' of a 60-degree offset is known?

Accepted Answer

1.155

Answer

The constant for calculating the travel of a 60-degree offset is 1.155. The formula is: Travel = Set x 1.155. The constant 1.414 is for 45-degree offsets, and 2.613 is for 22.5-degree offsets.

Journeyman Plumbers Exam Practice Test

Journeyman Plumbers Exam Practice Test

Journeyman Plumbers Isometric Analysis and Math Questions and Answers