The four things you will need to know are.
How to size roof storm drains.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
And 4 area handled by each drain.
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Determine 100 year 1 hour rainfall rate used for location of building.
The rain storm the flow of rainwater on the roof surface the ability of the roof drain to move the water from the roof to the piping the vertical piping the horizontal piping and the connection to the point.
From table a101 2 a 12 inch wide weir with a.
4 select a reference of a roof drain size with hourly rainfall together with the roof area square footage you have estimated and then determine from the chart below how many roof drains you require.
Enter table a101 2 to find a length and head that will carry 4 500 sq ft or more.
Take the roof s total square footage and divide by the total square footage handled by one drain.
Rate of rainfall would.
Size vertical storm drainage piping.
The above sizing data is offered as a guide only.
The full flow capacity of a drain is not realized until the water reaches approximately 2 5 above the inlet in a four inch drain and 3 5 in a six inch drain.
The sizing of the roof drainage system must consider all components.
1 rate of precipitation.
That is what is wrong.
Select number of roof drains and calculate the roof area sloped to each drain.
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.
1 4 in ft slope building storm drain 2 500 4 x 7 2 9 375 sq ft 4 500 sq ft.
Sizing data for conventional drainage storm drainage sizing precipitation rate inches hour based on 15 minute precipitation zurn makes it easy to size roof drains.
In a roof drainage system you have many components.
Each scupper is draining 2 500 sq ft of roof area.
Calculate drains needed.
The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains.
To convert this roof area to an area for use with table a101 2 do this.
Size horizontal storm drainage piping.
The result is the number of drains needed.
Using figure 8 the 312 g p m.
Ipc provides four steps to size the roof drains on a building.
3 size of leader required.
The pipe sizing is only one component.