How Do You Calculate Rainwater Discharge On The Roof And Its Pipe Size?
This falls within the practice of Mechanical engineering, check with them, barring that, the “Manual of Low-Slope Roof Systems” (Griffin and Fricklas) includes some methods for pipe sizing, but the tables listed above for maximum rainfall intensity by someone else will be useful. Typically the drain leader turns horizontal (well, slopes to the drain leader at 1/4″ per foot or so) below the roof and this reduces the capacity of the pipe. Florida has their own rules and the florida building code is online, from ecodes.com. If this is a real building, you should call a mechanical engineer to perform this task. An improperly designed roof can collapse and they usually leak and damage the property as well. A too small pipe will lead to pools of water on the roof and that is a weight the structural engineer may not have anticipated, particularly in heavy rainfall areas, you will need to track down a design standard that gives you a peak rainfall intensity for a one-hour storm, or whatever th
