Journeyman Plumbers Exam Isometric Drawings and Analysis 3

Question 1

Using an isometric drawing, a plumber measures a pipe run as 6 isometric inches long at 30°. What is the true horizontal length of that pipe?

Accepted Answer

6 inches

Answer

On a properly scaled isometric drawing, dimensions along the isometric axes represent true lengths, so 6 isometric inches equals 6 actual inches.

Question 2

A plumber needs to calculate a 45° offset using an isometric drawing. If the offset travel is 12 inches, what is the approximate run?

Accepted Answer

8.5 inches

Answer

For a 45° offset, the run equals the offset travel multiplied by 0.707, so 12 × 0.707 ≈ 8.5 inches.

Question 3

An isometric drawing shows a horizontal drain with a 1/4" per foot slope over a 20-foot run. What is the total drop?

Accepted Answer

5 inches

Answer

Total drop = 1/4" × 20 = 5 inches over the 20-foot horizontal run.

Question 4

When analyzing an isometric drawing for a parallel offset, which multiplier is used to find the diagonal travel for a 22.5° offset?

Accepted Answer

2.613

Answer

For a 22.5° offset, the travel multiplier is 2.613, applied to the offset distance to find the fitting-to-fitting diagonal length.

Question 5

An isometric drawing shows a 60° offset on a 3-inch pipe. If the set (offset distance) is 9 inches, what is the approximate travel?

Accepted Answer

10.4 inches

Answer

For a 60° offset, travel = set ÷ sin(60°) = 9 ÷ 0.866 ≈ 10.4 inches.

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