Abstract: A self-cleaning straining valve having an inlet, an outlet, and a flush port, in which a rotatable plug has a plug flow passage therethrough, the plug flow passage has, in addition to first and second openings at its two ends, a third opening therefrom through the plug wall, and first and second filter areas are respectively positioned in the first and third openings, the third opening communicating with the valve inlet and the first opening communicating with both the inlet and the flush port when the plug is rotated so that the valve is in a self-cleaning position, whereby in this self-cleaning position part of the incoming fluid from the inlet flows across the first filter area and then out the flush port, to clean the first filter area, and part of the incoming fluid passes through the second filter area, being filtered as it passes therethrough, then passes into the plug flow passage, and finally passes out through the first filter area and flush port, to backflush and thereby to further clean the first