Sizing a roof water drain.
Sizing roof leaders.
The above sizing data is offered as a guide only.
This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.
Calculate drains needed.
Take the roof s total square footage and divide by the total square footage handled by one drain.
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.
The result is the number of drains needed.
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.