Sizing Roof Leaders

Sizing a roof water drain.

Sizing roof leaders.

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

Calculate drains needed. 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 result is the number of drains needed. The above sizing data is offered as a guide only.