The pipe is primarily intended for use in transporting potable water in buried installations. The standard describes dimension ratios (DRs) 14, 18, and 25 for nominal pipe sizes ranging from 4 in. (100 mm) through 12 in. (300 mm). Pipe outside diameters (ODs) conform to those established for CI-equivalent ODs (CIOD). Pressure classes range from 165 psi (1,140 kPa) to 305 psi (2,100 kPa). Major changes made to the standard in this edition include the following: the factor of safety was revised from 2.5 to 2.0; the built-in surge allowance was eliminated; the pressure classes were revised from 100, 150, and 200 psi (690, 950, and 1,380 kPa) to 165, 235, and 305 psi (1,140, 1,620, and 2,100 kPa), respectively; treatment of surge pressures was expanded to include occasional (emergency) surge and recurring (cyclic) surge; and, Appendix B, Recurring (Cyclic) Surge - Figures and Design Example, was added.