A valve assembly for a machine for filling containers with a liquid has an adduction conduit extending along a valve axis and connectable to a tank of the filling machine to allow inflow of the liquid through a discharge mouth. A shutter arranged inside the adduction conduit and moving along the valve axis between a closing position and one or more opening positions has an annular gasket that with the shutter in the closing position sealingly engages an abutment seat. The annular gasket has a first annular portion for sealingly engaging a first portion of the abutment seat, and a second annular portion for sealingly engaging a second portion of the abutment seat. At least one flow window interrupts an annular continuity of the second annular portion and allows a partialized flow of liquid through the adduction conduit when the first annular portion is spaced apart from the abutment seat.