PVCO stands for molecularly oriented PVC. PVCO pipe starts as a piece of PVC pipe stock. During the manufacturing process, the PVC pipe stock is stretched over a mandrel to expand the pipe stock's diameter, this process is also referred to as biaxial orientation. The expansion of the pipe stock's diameter orients the PVC molecules in both the hoop and longitudinal orientation. The result of this biaxial orientation allows for the end product (PVCO pipe) to withstand greater stresses from internal pressure than it could before it was expanded. The final AWWA C909 PVCO product becomes stronger, tougher, and more flexible than traditional AWWA C900 PVC.