Journeyman Plumbers Isometric Drawings and Math Questions and Answers

Question 1

A plumber is installing a drain line with a simple horizontal offset of 24 inches using 45-degree fittings. What is the required center-to-center length of the travel piece?

Accepted Answer

33.94 inches

Answer

To calculate the length of the travel piece in a 45-degree offset, the formula is Travel = Run × 1.414. Given a run (the offset distance) of 24 inches, the calculation is 24" × 1.414 = 33.936", which rounds to 33.94 inches.

Question 2

An isometric drawing shows a rolling offset where a vent pipe rises 15 inches vertically and offsets 20 inches horizontally, using 45-degree fittings. What is the center-to-center length of the travel pipe required for this offset?

Accepted Answer

35.35 inches

Answer

This requires a two-step calculation. First, find the 'true offset' using the Pythagorean theorem (a² + b² = c²), where 'a' is the rise and 'b' is the horizontal offset. True Offset = √(15² + 20²) = √(225 + 400) = √625 = 25 inches. Second, calculate the travel piece by multiplying the true offset by the 45-degree constant: 25" × 1.414 = 35.35 inches.

Question 3

A journeyman plumber is installing a 3-inch horizontal sanitary drain that is 42 feet long. If the required minimum slope is 1/4 inch per foot, what is the total fall of the pipe over its entire length?

Accepted Answer

10.5 inches

Answer

To determine the total fall (or drop) of the pipe, multiply the length of the pipe run by the required slope per foot. The calculation is: 42 feet × 0.25 inches/foot = 10.5 inches.

Question 4

When interpreting a plumbing isometric drawing, a vertical pipe run is always represented by which of the following?

Accepted Answer

A true vertical line on the page.

Answer

In standard isometric drawing conventions, vertical pipes are always drawn as true vertical lines on the paper. Horizontal pipes are drawn at a 30-degree angle to the horizontal plane to give the illusion of three dimensions.

Question 5

A plumber needs to cut a piece of copper pipe to connect two 90-degree wrought copper elbows. The center-to-center measurement between where the fittings will be is 36 inches. The fitting allowance (take-off) for each elbow is 3/4 inch. What is the required end-to-end cut length of the pipe?

Accepted Answer

34 1/2 inches

Answer

To find the cut length of the pipe, the take-off for both fittings must be subtracted from the center-to-center measurement. The pipe fits into the sockets of the fittings. Calculation: 36" - (3/4" + 3/4") = 36" - 1 1/2" = 34 1/2 inches.

Journeyman Plumbers Exam Practice Test

Journeyman Plumbers Exam Practice Test

Journeyman Plumbers Isometric Drawings and Math Questions and Answers