After calculating the center to center measurement of an offset, the very next step is

• A. Add for the thread take up
• B. Multiply by 1.414
• C. Deduct for the fitting allowance from the center to center measurement
• D. Ignore the fitting allowance

Answer: (C)

When you’re planning an offset, the key measurement is the distance between the centers of the two pipe runs. But fittings themselves take up space along that path, so the straight length of pipe you actually need is shorter than that center-to-center distance. Subtracting the fitting allowance from the center-to-center measurement accounts for the space the fittings occupy, giving you the true length of pipe to cut for the offset. If you didn’t subtract this allowance, you’d end up with a pipe that’s too long or misaligned once the fittings are in place. Adding for thread take-up or multiplying by a diagonal factor isn’t part of this step, since those aren’t how offset lengths are determined.