To determine the correct length of pipe to cut for an offset, what must you do?

To determine the correct length of pipe for an offset, subtracting the fitting allowance from the travel is essential because it accounts for the space that the fittings will occupy. The travel is the distance between the two points the pipe will connect. However, when using fittings, such as elbows or tees, part of that travel is taken up by the fittings themselves, thus requiring an adjustment.

The fitting allowance represents the length added due to the fittings used to create the offset, which isn't part of the actual pipe length needed. By subtracting this allowance from the total travel, you ensure the cut length accurately reflects the straight pipe required to navigate the offset without any extra length that would not fit in the intended space. This calculation allows for precision in installation and avoids wasted material or misalignment in plumbing systems.