What calculation helps determine the length of the pipe to accommodate fittings?

To determine the length of the pipe needed to accommodate fittings, the calculation involves considering how much length is effectively added or altered by the fittings used in the plumbing system. When you subtract the fitting allowance from the true offset, you are accounting for the actual length of pipe that needs to be installed to achieve the desired alignment or direction of the piping system.

The true offset represents the actual distance between two points in a straight line, while the fitting allowance reflects the length that the fittings (like elbows, tees, etc.) will consume. By subtracting the fitting allowance from the true offset, you identify the correct length of pipe that remains between the fittings, ensuring that the installed system will align properly without surplus or deficiency.

This calculation is essential for ensuring accuracy in installing plumbing systems, as it helps avoid issues related to inadequate lengths or excessive materials, which can lead to leaks and improper fittings later on in the installation process.