Rainwater drainage system

The sizing process of a rainwater system can be divided into the following steps:

1. Calculation of roof surface. For each roof has different effective surfaceA, besides Ah is the horizontal projection of the roof area, Av is the vertical projection.

For single pitched roof with adjacent vertical wall: A = Ah + 0.5*Av

For single pitched roof: A= Ah + 0.5*Av

For flat roof: A=Ah

2. Calculation of the flow collected on the roof. Flow rate Q = r*A*c1*c2, in which r=0.04l/s/m2 , c1=1, c2=1. So we got the top roof flow rate and underground garden flow rate listed in the chart.

3. Sizing of rainwater downpipes according to the flow rate of each outlet.

4. Sizing of rainwater collector pipes.