Which of the following pipes is most likely to require joint restraint?

Ductile iron pipes are most likely to require joint restraint due to their inherent characteristics and the environments in which they are commonly used. These pipes are often installed underground in water distribution systems, where they can be subjected to significant hydraulic pressures and soil movements. Joint restraint is necessary in situations where there is a risk of the joints separating under these pressures, which could lead to leaks or complete system failure.

Ductile iron's strength and ductility make it a popular choice for water mains, but because of its weight and rigidity, it can behave differently under certain conditions compared to more flexible materials. In cases of high flow rates or when the pipeline encounters external forces, such as shifts in the surrounding soil, proper joint restraint becomes crucial for maintaining the integrity of the system.

In contrast, polyvinyl chloride (PVC), concrete, and high-density polyethylene (HDPE) pipes have different properties and applications that may reduce the need for joint restraint. PVC is lighter and more flexible, concrete is often used in gravity-fed systems with different load concerns, and HDPE can accommodate more movement, making them less likely candidates for requiring joint restraint in the same situations ductile iron would.