This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.
How to size roof storm drains.
The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains.
The result is the number of drains needed.
The sizing of the roof drainage system must consider all components.
The pipe sizing is only one component.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
And 4 area handled by each drain.
Select number of roof drains and calculate the roof area sloped to each drain.
In a roof drainage system you have many components.
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.
Take the roof s total square footage and divide by the total square footage handled by one drain.
Enter table a101 2 to find a length and head that will carry 4 500 sq ft or more.
To convert this roof area to an area for use with table a101 2 do this.
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System sizing data rainfall when expressed in g p m.
3 size of leader required.
1 4 in ft slope building storm drain 2 500 4 x 7 2 9 375 sq ft 4 500 sq ft.
Each scupper is draining 2 500 sq ft of roof area.
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.
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.
2 total area of roof.
The above sizing data is offered as a guide only.
Using figure 8 the 312 g p m.
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.
Calculate drains needed.
Determine 100 year 1 hour rainfall rate used for location of building.
1 rate of precipitation.
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 four things you will need to know are.
Size vertical storm drainage piping.
Size horizontal storm drainage piping.
From table a101 2 a 12 inch wide weir with a.
