Sizing a roof water drain.
Roof leader sizing.
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.
Enter table a101 2 to find a length and head that will carry 4 500 sq ft or more.
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.
When sizing roof drains the limiting factor for the amount of water each drain will carry away is the size of leader therefore increasing.
Rate of rainfall would.
Take the roof s total square footage and divide by the total square footage handled by one drain.
2 total area of roof.
The use of 4 x 5 downspout outlets starts at a depth of gutter of 4 5 inches.
The availability of 7 inch top width k style gutter has been poor in the past.
Or 12 drains required.
1 rate of precipitation.
1 inch 25 4 mm 1 gallon per minute 3 785 l m.
This corresponds to a minimum top width of 6 inches.
Use12 ichwdex5 inch high scuppers at four locations.
Using figure 8 the 312 g p m.
The flow rate through vertical leaders shall not exceed that specified in table 1106 3.
Vertical leaders shall be sized based on the flow rate from horizontal gutters or the maximum flow rate through roof drains.
System sizing data rainfall when expressed in g p m.
The above sizing is reflected in the development of figure 4 downspout outlet sizing leader pipe sizing.
3 size of leader required.
Can be applied to the table in figure 8 to determine the sizes of the various components of the conventional roof drainage system including roof drains vertical leaders and horizontal drainage piping.
The result is the number of drains needed.
This reveals that the minimum size for the leader pipe is 5.
But this isn t the whole story.
The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.
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.
2 500 4 x 7 2 9 375 sq ft 4 500 sq ft.
The four things you will need to know are.
This wizard makes it easy to calculate the roof design area by providing various shape calculations and the calculation for vertical walls area per international plumbing code ipc.
Table 1106 3 vertical leader sizing for si.
From table a101 2 a 12 inch wide weir with a inch head carries6 460 sq ft.
