A silly question really and I should know it. A relative's toilet cistern is only quarter filling and not enough to flush. I took the top off and by pressing the ball it fills up obviously. There is no adjustable screw on the valve to control the flow, however if you follow the rod along to the ball end there is a screw on the rod. Question is if I undo the screw and slide the ball further up the rod would it allow more water in?.