A 5 inch diameter pipe with a 1 4 inch per foot slope will carry 4 720 sq ft.
Horizontal roof drain pipe sizing.
Or less in diameter the piping will be larger in diameter than the roof drain.
The result is the number of drains needed.
Designers specify compliance with bs en 12056 3 2000 that includes a calculation for the allowable capacity of the rainwater pipes.
The roof drain or gutter or drain piping or downspout leader size diameter other size constraints e g.
This means that because our horizontal pipe from step 3 was 8 our vertical pipe will be also 8.
Or 12 drains required.
A minimum 5 inch diameter drain on a 1 4 inch per foot slope is required.
Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow.
The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain.
To convert to an area for use in table 1108 2 do this.
Roof drain connected to a 6 in.
Take the roof s total square footage and divide by the total square footage handled by one drain.
Roof drain connected to an 8 in.
The roof drainage outlets and rainwater downpipes are calculated based on the design principles for gravity drainage systems established in ss525 2006 code of practice for drainage of roofs.
For example in the u k.
The maximum number of drainage fixture units connected to a given size of horizontal branch or vertical soil or waste stack shall be determined using table 710 1 2.
In total square footage covered per drain 23 14 2 880 1 920 1 440 1 150 960 720 575 480 410 360.
Roof drain vertical requirement for horizontal roof areas at various rainfall rates leader size hourly rainfall in inches pipe open 1 1 1 2 2 2 1 2 3 4 5 6 7 8 size area inches sq.
Enter table 1108 2 until youfind a diameter pipe that will carry 4 688 sq ft.
5 000 4 x 3 75 4 688 sq ft.
Horizontal drain 5 000 sq ft.
The minimum size of any building drain serving a water closet shall be 3 inches.
Following this logic it is possible that for roof drains 6 in.
For example a 4 in.
Adequate drainage is an important component of a properly installed roof so installing the correct size of drains is essential.
For larger roof drains the pipe may be smaller such as a 10 in.
