OK, OK, I get it now!
I don't think coriolis force has any measurable effect on your experiment. We're talking pure centrifugal force here!
You say it took 4 turns to empty out the bag with the bend pointed towards the floor or the ceiling (i.e., at a 90° angle from the axis of rotation), whereas it only took 2.5 turns to empty the bag when the bend faced away from rotation.
The ratio of your experimental results is thus 4/2.5 = 1.6, the radian measure of a 90° angle is ∏/2 = 3.14159/2 = 1.570795.
In other words, this is centrifugal force as a function of angular velocity.
When the bend faced away from the axis of rotation, centrifugal force kept the bag from deflating.
The reason the 90° bend helped in your first experiment is because, relative to the axis of application of force, this is actually two 45° angles, which is the usual axis of application of a force: that's the principle underlying the corbel arch and the flying buttress! I can't believe I forgot that!
With the straight tube, the action of centrifugal force would have directed the water against the side of the tube opposite the action of rotation, which would have hindered, rather than assisted, the flow of water out of the ends of the tube.