The WFF filter is connected to a horizontally installed pipe of at least 1 metre in length, coming from the roof. Rainwater from the roof enters the filter at the side and is then guided over the vertically positioned cylindrical filter.

Due to centrifugal force, the rainwater is drawn through the vertical filter and directed via the rear outlet to the rainwater tank. The debris is carried away together with the residual water to the drain.

According to this principle, more than 90% of the incoming water is filtered. There are no narrow sections in the pipes or passages where water or debris could accumulate. This is particularly important during cloudbursts or heavy rainfall.

Even under these conditions, 50% of the incoming water is still filtered and discharged into the rainwater tank. The remaining water flows away via the drain.