What type of joint is used when assembling cast-iron soil pipes?

The correct choice involves the use of no-hub joints or bell-and-spigot compression for assembling cast-iron soil pipes. These types of joints are designed specifically to accommodate the material properties and installation needs of cast-iron pipes.

No-hub joints consist of a rubber gasket positioned between two pipes, secured with a stainless-steel band. This design allows for flexibility during installation and enables the pipes to expand and contract with temperature changes while maintaining a secure seal, which is crucial for ensuring leak-free connections in plumbing systems.

Bell-and-spigot compression joints, on the other hand, feature a bell end on one pipe that fits over the spigot end of another pipe. The design ensures a strong, tight fit that is essential for managing the flow of wastewater and preventing leaks.

Both methods provide durability and strength suitable for the weight and structural considerations of cast-iron soil pipes, making them the preferred choices for this application. The other options do not align with the preferred practices for cast-iron assembly or involve types of joints that are not typically used in that context.