Sizing Roof Leaders

Calculate drains needed.

Sizing roof leaders.

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. This reveals that the minimum size for the leader pipe is 5. The above sizing data is offered as a guide only.

Sizing a roof water drain. The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout. 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. 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.