What type of piping is supplied by the riser nipple from the cross main?

The correct answer indicates that a branch line is supplied by the riser nipple from the cross main. In a sprinkler system, the riser serves as a vertical section of pipe that connects the cross main to the branch lines. The cross main is typically a larger pipe that distributes water horizontally, while the branch lines extend off the cross main and deliver water to individual sprinkler heads.

In this context, a branch line is required to carry water from the riser nipple to specific areas needing sprinkler coverage, thus allowing for targeted fire suppression. The riser nipple is crucial in connecting these systems as it helps facilitate water flow from the larger distribution system (the cross main) down to the smaller branch lines that service specific zones or areas.

Understanding the relationship between these components is key to grasping basic sprinkler system design and operation, emphasizing the flow of water from larger mains to smaller, targeted applications in fire protection systems.