When a scupper is used as an overflow, drains must be?

When a scupper is utilized as an overflow, it is essential for the drainage system to be adequately sized to handle potential excess water flow during heavy rainfall or drainage system failure. The correct answer indicates that the drains must be three times the size of the roof drain. This sizing ensures that there is enough capacity in the overflow drains to accommodate the increased water flow and prevent flooding or pooling on the roof surface.

The need for drains to be larger than the primary roof drain reflects the principle of redundancy in drainage systems. It maintains structural integrity and safety by allowing for effective water management. This design consideration is crucial, especially in systems where heavy precipitation can rapidly overwhelm the primary drain.

Sizing drains to three times the size of the roof drain serves as a safety margin, ensuring that even in scenarios where the roof drain is at capacity, the overflow can efficiently handle additional water, directing it away safely and minimizing damage to the building or roof structure.