Roof drain selection.
Roof drain leader pipe.
This is where the rainwater is lead away from the building s foundation so that no rainwater is able to pool around the building.
In general increasing leader size will decrease the number of drains required.
Downspouts are usually vertical and usually extend down to ground level.
Use this downspout extension to divert water away from the foundation or connect to drainage pipe and catch basin to control drainage.
Divide roof area 1 by area per leader 4 to determine the number of drains required.
This flexible downspout extension easily bends and holds its shape and can be extended from 25 55 in.
Reference leader size with hourly rainfall rate to determine roof area drained by each leader chart b.
Table 1106 2 storm drain pipe sizing for si.
The flow rate in storm drain piping shall not exceed that specified in table 1106 2.
The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.
Sizing a roof water 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.
Approximate leader drain pipe size.
There is generally a bend of 70 degrees at the bottom.
Vertical and horizontal storm drain piping shall be sized based on the flow rate through the roof drain.
1 inch 25 4 mm 1 foot 304 8 mm 1 gallon per minute 3 785 l m.