The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains.
Roof drain conductor sizing.
Table 1106 2 storm drain pipe sizing for si.
The flow rate in storm drain piping shall not exceed that specified in table 1106 2.
The result is the number of drains needed.
The end result is roof drains 6 in.
This reveals that the minimum size for the leader pipe is 5.
The next step is to determine each roof area that will be served by a separate leader drain pipe scupper or downspout.
Section 101 5 of the ipc tells us not to reduce the pipe size in the direction of flow.
Or smaller in size have the ability to flow more water to the piping than the piping can handle using 33 for the vertical and full flow for the horizontal.
1 inch 25 4 mm 1 foot 304 8 mm 1 gallon per minute 3 785 l m.
As it turns out the opposite is true of most roof drains.
Vertical and horizontal storm drain piping shall be sized based on the flow rate through the roof drain.
Take the roof s total square footage and divide by the total square footage handled by one drain.
To convert to an area for a 4 inch per hour rainfall to enter table 1108 1 do this.
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.
Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.
Or 12 drains required.
Step by step sizing of zurn drains step 1 a.
Each vertical drain must carry 2 500 sq ft of roof area at 3 75 inches per hour of rainfall.
Calculate total roof area.
50 000 4 400 11 36.
Example roof plan 4 a 101 2 solution.
The flow through the roof drain is very efficient directing the water into the drain.
Factors which affect proper roof drainage are deck slope drain size and placement of drains.
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.
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.
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.
2 500 4 x 3 75 2 344 sq ft.
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 sizing for the horizontal piping is based on the pipes flowing full.
