How To Size Roof Storm 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.

How to size roof storm drains.

Rate of rainfall would. 1 rate of precipitation. Enter table a101 2 to find a length and head that will carry 4 500 sq ft or more. Calculate drains needed.

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. 2 total area of roof. Size horizontal storm drainage piping. To convert this roof area to an area for use with table a101 2 do this.

From table a101 2 a 12 inch wide weir with a. 3 size of leader required. In a roof drainage system you have many components. Roof drainage 2016 05 11 plumbing advanced drainage systems sizing a gravity pipe work water surface pros for storm sewers sizing a gravity pipe work four s to sizing roof drains c1scapacities of sewer pipespipe sizing charts tables energy modelsdrain and sewer pipe size home owners workfour s to sizing roof drains c1scapacities of sewer.

And 4 area handled by each drain. 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 scupper is draining 2 500 sq ft of roof area. 1 4 in ft slope building storm drain 2 500 4 x 7 2 9 375 sq ft 4 500 sq ft.

Using figure 8 the 312 g p m. The sizing of roof drains must be large enough to quickly carry away all water entering the roof drains. Select number of roof drains and calculate the roof area sloped to each drain. 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 above sizing data is offered as a guide only. Take the roof s total square footage and divide by the total square footage handled by one drain. System sizing data rainfall when expressed in g p m. Each 4 drain size in a 6 hourly rainfall area will accommodate drainage of 3 070 sq.

The pipe sizing is only one component. The sizing of the roof drainage system must consider all components. The four things you will need to know are. Determine 100 year 1 hour rainfall rate used for location of building.

Size vertical storm drainage piping. The result is the number of drains needed. 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.