That is what is wrong.
How to size roof leader collection pipe size.
Take the roof s total square footage and divide by the total square footage handled by one drain.
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.
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.
Each drain will carry away is the size of leader therefore increasing leader size decreases the number of drains required.
For the purposes of this appendix the following metric conversions are applicable.
The sizing of the roof drainage system must consider all components.
1 calculate the roof area to be drained.
Rate of rainfall would require a 5 inch roof drain and leader as well as a 6 inch horizontal drainage line if a slope of 1 4.
Calculate total roof area.
The above sizing data is offered as a guide only.
In sizing roof drains and storm drainage piping one half of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors leaders and horizontal storm drainage piping.
300 x 500 150 000 sq.
This table is based on zurn s roof drain vertical requirement for horizontal roof areas at various rainfall rates table.
Roof area is 300 x 500 ft.
According to the chart for 1 8 slope per 12 of pipe for 5 000 square feet of roof area with a 6 per hour of rainfall the required pipe size is 8.
In a roof drainage system you have many components.
1 in 25 4 mm 1 ft 305 mm 1 ft2 0 0929 m2 100 0 figure a101 1 example roof plan 4 a 101 2 solution.
The pipe sizing is only one component.
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.
4 leader size is selected.
Using figure 8 the 312 g p m.
Step by step sizing of zurn drains step 1.
Roof area is 200 x 500 100 000 sq.
The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.
Roof drain system and size the scuppers denoting the required head of water above the scupper for the structural engineer.
The result is the number of drains needed.
Calculate drains needed.
2 estimate the roof drain outlet size you will likely use.
Determine the size of leader to be used.
