I understand the IVP guys with winglets make a nice big loop above the NACA for a water trap.  The standard wingtips don't allow for any rise above the vent inlet, since the vent inlet in the wing is on the upper skin surface.  My tubing does a 270 degree turn, pretty flat.

 

Maybe I'm missing something, but if the engine suction can buckle the wing skins, couldn't it suck a small amount of water through the tube?  Then the water would settle to the bottom of the tank and get sumped out at the next preflight.  It would take a decent amount of water to rise high enough to get into the fuel outlet to the engine, right?

 

Mike Easley

Colorado Springs