Yes, but with water touching the internal faces too, again there is a net torque on the screw as you said before. But again the gaskets cancel the torque. If the gaskets thickness is much less than the screw thread, much of the forces on the thread is canceled by the forces on other side of the thread the remaining is canceled by the gaskets. If the thickness ratio is not small, again the number of gaskets must be large.
My problem now is with the case of the rigid gaskets fixed to the water container ( pipe). I have no explanation for this yet.
by the way, what software do you use for draw such figures?