Sizing Roof Leaders

This reveals that the minimum size for the leader pipe is 5.

Sizing roof leaders. The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout. The first step in sizing a roof drain is to calculate the surface area of the roof that the drains will be covering as well as the average hourly rainfall rate at the building location. Calculate drains needed. The result is the number of drains needed.

Take the roof s total square footage and divide by the total square footage handled by one drain. To size the vertical roof drain for the same parameters 5 000 square feet of room area and 6 per hour of rain consult table 1106 2 figure 3. In sizing roof drains and storm drainage piping one half of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors leaders and horizontal storm drainage piping. This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.