The National Roofing Contractors Association defines scupper as "A drainage device in the form of an outlet through a wall, parapet wall or raised roof edge typically lined with a sheet-metal sleeve." It is more often seen in apartments and other commercial buildings, though is sometimes found in residential homes constructed with flat roofs.
A roof scupper is a roof drainage system that provides drainage of a flat roof by allowing the water runoff from the roof to exit the roof through a metal edge, parapet wall or through the deck into a downspout or leader. Roof scuppers are not the same as roof drains. Roof drains channel water through the deck of the roof into a piping system that carries water away, while a scupper allows water to drain through an opening in the side of the roof edge.
If a roof scupper becomes blocked or clogged and prevents water from draining from the roof surface, this could cause ponding or roof leaks. Cleaning and checking your roof drainage system is an important roof maintenance item.