Abstract: A pump for pumping a liquid containing solid contaminants, which pump comprises rotatable pumping means for pumping the liquid from a pump inlet to a pump outlet, a filter for filtering the liquid, auxiliary pumping means for pumping the liquid to the filter, first passage means for passing filtered liquid to at least one bearing in the pump for lubrication, a rotor device which is operative during use of the pump to cause the liquid inside the filter to swirl and clean the inside of the filter, and second passage means for allowing the passage of unfiltered liquid from the inside of the filter whereby the unfiltered liquid can remove separated solid contaminants on the inside of the filter.