A three-phase solid bowl screw centrifuge includes a rotatable drum, a screw arranged in the drum, a solid material discharge located at the fist axial end of the drum, and two liquid outlets are located at a second axial end of the drum. A first of the liquid is for a lighter liquid phase and a second of the liquid outlets is for a heavier liquid phase. One of the liquid outlets includes a skimmer disk arranged in a skimmer chamber and the other of the liquid outlets is formed as an overflow. Two regulating disks are located in the front of the skimmer disk. The regulating disks extend radially from an outside of the drum toward an inside of the drum. A siphon disk extends between the regulating disks and into the skimmer chamber from a interior circumference of the skimmer chamber to an exterior circumference of the skimmer chamber. An annular chamber is formed during an operation and is located between the siphon disk and the skimmer disk.