<p>PCT No. PCT/GB91/01889 Sec. 371 Date Apr. 28, 1993 Sec. 102(e) Date Apr. 28, 1993 PCT Filed Oct. 29, 1991 PCT Pub. No. WO92/08059 PCT Pub. Date May 14, 1992.A vortex valve includes a housing having a cylindrical side wall and opposite ends to define a vortex chamber. The sidewall of the housing has a primary tangential inlet through which liquid may enter the vortex chamber in a manner to promote swirl within the vortex chamber and an outlet at one axial end of the vortex chamber. The outlet represents at least 50% of the area of the end of the vortex chamber in which it is situated and in the vortex chamber has a length which is at least one and a half times the diameter of the outlet. The vortex valve requires only a low head to initiate vortex flow.</p>