Which of the following is a type of joint for ductile iron piping?

The type of joint commonly used for ductile iron piping is the flanged joint. Flanged joints are particularly advantageous because they allow for easy assembly and disassembly of pipes, which is essential for maintenance and repairs. This type of joint consists of two flanged ends that are bolted together, providing a strong, leak-proof connection that can accommodate various alignment conditions.

Additionally, flanged joints can be used in a variety of applications, including water distribution, and they facilitate the attachment of valves, fittings, and other components in the piping system. The robust nature of the flanged connection is particularly suitable for the physical and operational characteristics of ductile iron pipes, making it a streamlined choice for engineers and contractors working with this material.

Other joint types, while relevant in different contexts, do not align as directly with the common practices associated with ductile iron piping. For instance, welded joints are more typical for steel piping and require special skills and equipment, while bell and spigot joints are often found in other types of pipe systems like clay or PVC. Expansion joints provide flexibility for thermal movement but are not specific to ductile iron piping. Thus, the flanged joint is the preferred and most representative choice for ductile iron applications in water distribution.