The figure above is a schematic diagram of a rotating lawn sprinkler as seen from above. Water is injected into the central hub and squirted out the bent tubes as shown by the arrows. This causes the sprinkler to rotate in a clockwise direction as shown by the curved arrow at the top of the figure.
My question is as follows: Suppose the sprinkler were placed at the bottom of a pool and the hub were connected to a suction pump. This pump would then suck water in through the inlets in a direction opposite the arrows shown. In what direction would the sprinkler rotate, counter clockwise or clockwise? I believe that it would still be clockwise.
My argument is that as the water enters the tubes it has to make a right angle turn. This causes the water to transfer momentum to the tubes in a direction that causes the sprinkler to rotate clockwise. Does anyone have a counter-argument?