Temperate climate zone or tropical climate?
The roof area that can be connected to utilise rainwater depends on the local rainfall, as significantly different values are to be expected in the tropics, for example, than in temperate climate regions.
But there are also considerable differences within a climate zone. The decisive factor is the diameter of the drainage pipes.
The architect plans the pipe diameter
When constructing a new building, the diameter of the drainage pipes is determined by the architect or planner. He takes into account the local climatic conditions and the size of the connected roof area.
Determine the diameter yourself
If the rainwater filter is retrofitted, the diameter of the existing pipes is decisive. Depending on the installation position, it can be the (almost) horizontal sewer base pipe (KG pipe) in the ground or the vertical downpipe.
For the sewer base pipe
KG pipes are standardised in the DN standard to match our rainwater filters. The outer diameter of the pipes is crucial for a precisely fitting connection. It is often stated on the pipe or can be measured with a sliding gauge.
For the downpipe
If the DN specification is not directly on the downpipe or pipe clamp, you can measure it yourself. You can find out the easiest way to do this in the following article:
Determine downpipe diameter