What is the size of the pipe needed for section "A" of the Roof Drainage system, assuming a fall of 1/8" per foot and a 4 inch per hour rainfall?

The size of the pipe needed for section "A" of the Roof Drainage system must accommodate the volume of water expected from a rainfall of 4 inches per hour while maintaining an adequate fall of 1/8 inch per foot.

To determine the appropriate pipe size, it’s essential to consider the capacity of different pipe diameters to handle stormwater runoff effectively. A 6-inch pipe is commonly recommended for scenarios involving significant rainfall, such as 4 inches per hour, because it has enough diameter to allow for swift water flow and prevent overflow or blockages. The 1/8 inch per foot slope aids in ensuring that water moves smoothly towards the drain, minimizing the chances of pooling.

Larger pipes like an 8-inch would certainly handle the flow, but might not be necessary unless extreme conditions are anticipated, which are not indicated here. Smaller pipes like 4 or 5 inches may lead to inadequate drainage, risking overflow during heavy rainstorms.

In this instance, selecting a 6-inch pipe strikes a balance between capacity and practicality for the specified conditions.