I can't say it's not possible because anything you can think of is, but you would have to work pretty hard at it to get intrapped. The antivortex covers are screwed down so that a screwdriver is needed to remove them and are solid on top so the water flows in from the sides only. Pretty difficult to cover that.... Now you have two of those 3' apart. So it would either take a 4' wide person, or someone would have to lay accross both of them to try and cover the openings on the perimeters of the drain..... or..... it would take two people to do so at the same time.

Oh... now some states are requiring a vent line attached to the suction line in addition to the two MDs in the event the almost impossible scenario I described above happens.

Any thoughts or comments on this??