Ok but I would like to understand this particular problem in details ;)
I put two 3D drawings:
1/ a zoom of the bottom of the thread (yellow), we can see the difference of altitude of the thread and this show there is a torque with external/internal surfaces,
2/a zoom of the thread in sandwich with anothers fixed thread. I put the gasket extremely thin 1Ám between yellow and grey threads. This don't cost energy. And inside (the volume create by gaskets which is between up/down surface and grey surface) there is no water only air.
I have questions:
a/ are you agreed with the torque with only 2 surfaces external/internal (don't think at another surfaces) ?
b/ Why do you think the torque is proportional with the thin of the torque ? The thickness of the square thread don't change with the thickness of the gasket.
c/ orange color of your drawing is gasket for you ? Because for me not at all. See for that the zoom.
Thanks for your help ;)