Abstract: A header conduit provides an elongated passageway through which waste liquid and sludge ("waste") are guided and enter the conduit along a path that is tangential to at least the inner surface of the conduit which such incoming waste first contacts. When the conduit has an inner surface of circular cross-section, the passageway is elongated enough that the incoming waste enters the conduit along a path tangential to the circular surface. To better assure axial flow of the waste in the conduit to an outlet, the passageway provides both the tangential flow and is at an acute angle to the longitudinal axis of the conduit. The incoming waste is thereby provided with an axial component. In this manner, the passageway assures that the energy and momentum of the incoming waste is helical in direction. The waste previously admitted into the header conduit is urged by the newly entering waste to continue to flow helically in the conduit.