Which of the following pipe materials is typically considered non-flexible?

Steel is typically considered a non-flexible pipe material due to its inherent properties. Unlike thermoplastics or polyethylene (PE), which can bend and adapt somewhat under pressure or temperature changes, steel is rigid and maintains its shape under normal operational conditions. This rigidity makes steel an excellent choice for applications that require structural integrity and resistance to deformation, such as in high-pressure water distribution systems.

Ductile iron, while it also retains some rigidity, does have a degree of flexibility compared to steel, making it more adaptable in certain situations. However, the primary factor that defines steel as non-flexible lies in its strength and inability to easily bend without significant force applied, thus making it a reliable choice for long-lasting installations while minimizing deformation risks.