How To Size Roof Storm Drains

Determine 100 year 1 hour rainfall rate used for location of building select number of roof drains and calculate the roof area sloped to each drain size horizontal storm drainage piping size vertical storm drainage piping.

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. Or less in diameter the piping will be larger in diameter than the roof drain. For multiple walls use 50 percent of the maximum projected area of all walls.

Calculate total roof area. For example a 4 in. 2 total area of roof. Calculate the total roof area by multiplying its length by width.

The four things you will need to know are. 3 size of leader required. To convert to an area for a 4 inch per hour rainfall to enter table 1108 1 do this. 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.

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. And 4 area handled by each drain. For drain areas between two opposite walls add no additional area. The four things you will need to know are.

3 size of leader required. Zurn makes it easy to size roof drains. 2 3 4 5 6. 2 3 4 5 6 and 8 in.

2 total area of roof. Each vertical drain must carry 2 500 sq ft of roof area at 3 75 inches per hour of rainfall. Roof drain connected to an 8 in. For horizontal pipes or leaders receiving two or more roof drains.

Step by step instructions step 1. If the area of each wall is not the same add 50 percent of the difference between the two areas. Following this logic it is possible that for roof drains 6 in. 1 rate of precipitation.

Ipc provides four steps to size the roof drains on a building. Determine leader or pipe size. 2 500 4 x 3 75 2 344 sq ft. 1 rate of precipitation.

For larger roof drains the pipe may be smaller such as a 10 in. 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. A minimum 4 inch vertical drain is required.