A scupper is best known as a maritime term that refers to an opening cut through the bulwarks of a ship that allows water on the deck of the ship to flow overboard. Virtually all ships, as well as boats large enough to have decks above the waterline, are made with some form of scupper. These often include flap or ball designs that enable water to flow off of the decks, but not back into the ship should the scupper opening dip below the waterline in high seas or rough waters.
The word scupper also refers to a fitting or opening in the parapet or gravel stop of a level roof that allows rainfall or snow melt to drain off of the roof. This can help prevent leakage or structural damage to the building below. Sometimes scuppers are connected directly to rain gutters and downspouts. In other cases, they extend beyond the surface of the outer wall, creating a flow of water away from the building.
Generally, a scupper can be any opening that allows water or other fluids captured in a containment vessel on one level to flow outward to a lower container or body of water. In many settings, they are part of designs known as water-in-transit systems. This phrase refers to a system where water flows from one level to another for either decorative or functional purposes.
Many scupper designs include some form of conductor head — the structure where water or some other type of fluid is collected — and a weir or spout — the passage through or over which the fluid flows and is transmitted to a lower level. Scuppers can be massive structures, such as the overflow channels used in reservoirs and dams to prevent flooding, or extremely minute, such as chemical reservoir systems used in pharmaceutical manufacturing. Also, scuppers are commonly used on bridges and highways to prevent structural damage and to conduct standing water away from busy thoroughfares.
Scuppers of various types are also used in decorative applications, such as swimming pools, fountains, decorative troughs, and reflecting ponds where water moves in transit from one level to another. The size, shape, and materials of these scuppers are often designed to combine with the appearance and sound of moving water to create specific architectural and design effects. Scuppers can be made from any number of materials, including stainless steel, plastic, polymers, polyvinyl chloride (PVC), bronze, copper, sheet metal, marble, and other types of stone.