What is the name for the exterior drainage pipe that carries storm water from roof drain systems?

The correct choice describes the exterior drainage pipe that efficiently directs storm water away from roof drainage systems. The term used for this is "leader." Leaders are designed to handle and transport water that collects from roof surfaces, guiding it from the roof down to ground level or into a drainage system, ultimately preventing water accumulation around the foundation of a building.

In contrast to the other options, a downspout is a specific type of leader that connects to the gutter system and allows the flow of rainwater to the exterior drainage system. A drain pipe usually refers to an underground pipe system that carries wastewater, while a gutter is the component that collects and channels rainwater from the roof to the downspout or leader. Understanding these distinctions clarifies the role of each component in drainage systems.