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But if the tube the water comes out of is pitched, the weight will be heavier on one side and influence the direction of flow.
Being in construction, if the water went clockwise I would want to know if the toilet was out of level with the right side lower than the left.. and vice versa.

As Pat mentioned, I also think brand (and model) would be a factor. American Standard here (2) both clockwise when viewed from above. I'll have to get out the level later.



I think you may have hit the nail on the head. The symmetry of toilets is such that I think there would be very little vaning effect from the surface, and even minimal from the water flowing into the bowl.

However, two things I'd expect to make a notable difference are :

1) the level of the toilet (If it aint level, then the water exits at some angle)
Thanks Bob, for pointing that out. That's an easy one to check.

2) and the random direction the plumber chose to orient the trap. Water molecules are cohesive, so if the water takes a turn anywhere in the process of exiting the premises, the molecular cohesion could exert an influence on everything coming behind it.

Now I'm tempted to tear out the ceiling under the bathrooms to see if the orientation of the trap coincides with the rotation of the water in that toilet.

(apparently I *DO* have too much time on my hands... but hey, its Saturday)

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0