Roof Area Per Roof Drain

Determine leader or pipe size.

Roof area per roof drain.

Doubling the number of downspouts halves the required capacity for each. Roof drainage systems need to be designed to cope with the rainfall intensities for the specific building location. Drainage design specific to location. Step by step sizing of zurn drains step 1.

The roof drain calculator below is based on the maximum amount of rainfall in inches per hour of the hypothetical worst storm in the past 100 years and which has a two percent chance of occurring in any given year. Size downspouts to fit the gutter. 300 x 500 150 000 sq. Calculate total roof area.

To a depth of 1 in 1 hour. A square inch of downspout can drain 1 200 square feet of roof during a rain with an intensity of one inch per hour. Determine rate of rainfall for this example use 4. Calculate total roof area.

Divide the total roof area by the area that one leader will handle. Walls that drain onto a lower storey roof can increase the effective roof area by around 50. There are 5 easy steps to figure out how many drains your commercial roofing project will need. 1 inch of rainfall in an hour will cover 1 sq ft.

Roof area is 200 x 500 100 000 sq. Converting this to gallons per minute per square foot gpm ft 2. 4 roof drain 3 determine your building s location on the above map to determine the approximate rainfall as measured in inches per hour. Roof area the locale s rainfall intensity and gutter capacity determine how many square inches of downspout are needed.

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. If the result is a fraction less use the next higher number. The above result is the number of roof drains required for the building. Roof area is 300 x 500 ft.

Calculate the total roof area by multiplying its length by width. 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. The speed at which the rain collects at the drain. Rainfall intensities vary throughout new zealand and are often very high.

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.