Abstract: A method and apparatus for cleaning a permeable, hollow membrane (7) in an arrangement of the type wherein a pressure differential is applied across the wall of the permeable, hollow membrane (7) immersed in a liquid suspension, the liquid suspension being applied to the outer surface of the permeable hollow membrane to induce and sustain filtration through the membrane wall, the method of cleaning comprising the step of producing mechanical agitation between the membrane and the liquid suspension to dislodge at least some of the solids retained in or on the membrane. Application of the pressure differential by force of gravity applied to the liquid is also disclosed.