A minimum 4 inch vertical drain is required.
Roof drain pipe size.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
Calculate total roof area.
Therefore the 100 000 sq.
Take the roof s total square footage and divide by the total square footage handled by one drain.
The result is the number of drains needed.
Roof drain connected to an 8 in.
When sizing roof drains the limiting factor for the amount of water each drain will carry away is the size of leader therefore increasing leader size decreases the number of drains required.
300 x 500 150 000 sq.
Unfortunately recommendations aren t that straightforward because you also need to account for water pressure material friction and more.
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.
For larger roof drains the pipe may be smaller such as a 10 in.
For example a 4 in.
Each vertical drain must carry 2 500 sq ft of roof area at 3 75 inches per hour of rainfall.
Or 12 drains required.
But this isn t the whole story.
Enter table 1108 1 until you find a diameter pipe that will carry 2 344 sq ft.
Determine the size of leader to be used.
The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.
Following this logic it is possible that for roof drains 6 in.
Step by step sizing of zurn drains step 1.
Roof drain connected to a 6 in.
Sizing a roof water drain.
This reveals that the minimum size for the leader pipe is 5.
Area roof will require 100 000 3070 32 5 or 33 roof drains for ideal drainage.
Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow.
50 000 4 400 11 36.
We regularly get asked about the water flow capacity of different pipe sizes and which is the best roof drain for a specific pipe size.
The calculations below are meant for drainage from flat roofs where water are expected to spread over the entire flat roof during rain.
Pipe size in inches vertical drain gpm 1 16 per foot gpm 1 8 per foot gpm per foot gpm per foot gpm 2 34 15 22 31 44 3 87 39 55 79 111 4 180 81 115 163 231 5 311 117 165 234 331 6 538 243 344 487 689 8 1 117 505 714 1 010 1 429 10 2 050 927 1 311 1 855 2 623 12 3 272 1 480 2 093 2 960 4 187 15 5 543 2 508 3 546 5 016 7 093.
Roof area is 300 x 500 ft.
To convert to an area for a 4 inch per hour rainfall to enter table 1108 1 do this.
Or less in diameter the piping will be larger in diameter than the roof drain.
