The proper installation of screw pipe work requires getting correct and accurate measurements. Every plumber is or should be able to get correct center to center, center to end, end to end, center to back, and end to back measurements. In Durham work 45°; angles are continually occurring. To get these measurements correctly, the following table has been compiled as used by the author and found to be correct. The reader should memorize it so that it may be used without referring to the book.

### Measurements

Soil pipeScrew pipeMultiplier
1⁄6 bend601.15
1⁄8 "451.41
1⁄12 "302.00
1⁄16 "221⁄22.61
1⁄32 "111⁄45.12
1⁄64 "55⁄810.22

Before any measurements are taken, the lines of pipe are laid out and the position of each fitting known. As I have stated before, the plumber must look ahead with his work. He must have the ability of practically seeing the pipe in place before the work is started. This requires experience and judgment. Before the measurements are taken and the pipe cut consideration must be given to the fact that the fittings and pipes must be screwed into position. Therefore, "can the fitting on the pipe be placed where it is laid out when this is considered?" must be one of the many questions a plumber should ask himself. Allowance must be made for the chain tongs to swing. Whenever possible, a fitting is made up on the pipe while the pipe is in the vise.

Fig. 76. - The offset is B or 12 inches center to center. The offset is made using 45 degree fittings. Therefore the length of A from the center of one fitting to the center of the other is B × 1.41 = 12 × 1.41 = 16.92 inches.