Flow controlling device for a discharge system such as a drainage system

A flow controlling device for a discharge system, such as a drainage system, comprising a first vortex chamber (101, 201, 301, 401, 501) with an inlet (102, 202, 302, 402, 502) and an outlet (103, 203, 303, 403, 503) and a second bigger vortex chamber (110, 210, 310, 410, 510) with a peripheral inlet and a central outlet axial in relation to a vortex in this chamber, said second vortex chamber being at the peripheral inlet connected to the outlet (103, 203, 303, 403, 503) of the first vortex chamber (101, 201, 301, 401, 501b), wherein the first vortex chamber (101, 201, 301, 401, 501) is symmetrical with respect to a median plane perpendicular to a vortex axis (A), the direction of both the inlet (101, 201, 301, 401, 501) and the outlet (103, 203, 303, 403, 503) being parallel with said median plane, the first vortex chamber being asymmetric with respect to a plane parallel with the inlet direction and perpendicular to said median plane, the vortex axis (A) of the first vortex chamber (101, 201, 301, 401, 501) being perpendicular to a tangent of the second vortex chamber (110, 210, 310, 410, 510) at the peripheral inlet and the ratio between the diameters of the first vortex chamber and the second vortex chamber is less than 0.43:1.