Hmmm,,,,,,,,,,,,
Edit:
Sorry Rich, the res is passive
think about it and you will see what I mean
Picture a bucket of water with no lid, as long as the water level is above the intake and outtake it remains passive
I do understand what your though process is here, one could argue the loop would drain onto the res, and even overflow it, but with the lack of air behind it gravity is just an idea.
Example.
Take a straw, dip it into your soda, when you pull it out their is no soda in the straw, leaving density out of the equasion.
Now if you put your finger over the end of a straw and pull it out the gravitaional pressure measured at 14PSI and change is not present, hence you see the soda is still in the straw & you can get a nice cold drink with out picking up the glass ......
Not sure if this makes any sense at all though and I may just be babeling ............
