a housing arranged about a longitudinal axis and including a continuous inner surface defining a fluid flow path for liquids or gases, an inlet to the fluid flow path, and an outlet from the fluid flow path; and

a helical member extending longitudinally through said fluid flow path and helically about the longitudinal axis between the inlet and the outlet, the helical member comprising an intake end open to the inlet, a discharge end open to the outlet, an outer surface between the intake end and the discharge end and facing the continuous inner surface, an inner surface between the intake end and the discharge end and facing the fluid flow path, deflectors each projecting inwardly into the fluid flow path from the inner surface of the helical member, the helical member elastically expansive, being tensioned outwardly toward the continuous inner surface exerting outwardly directed pressure by the outer surface directly against the continuous inner surface frictionally securing the outer surface to the continuous inner surface securing the helical member to the housing.