A corrugated pipe is a pipe with a series of ridges and grooves running parallel to each other on its surface. The ridges and grooves follow a pattern that is perpendicular to and bisecting the centerline of the pipe. Corrugated pipes are made of different materials such as iron, steel, polyvinyl chloride (PVC), or high-density polyethylene (HDPE). Corrugated pipes are used where flexibility is an important factor other than strength and durability, such as in storm drains and culverts. Flexibility makes corrugated pipes more useful and suitable for a wide variety of uses compared to rigid and non-corrugated pipes.