If the unit was designed to draw water from the tank, divert it to the right of the filter housing from the bottom of the media and up out the overflow, then why is there a water filled space to the left of the media basket? /quote]
So it can't plug up and overflow onto the floor...it'll overflow into the return side and the back into teh tank.
all the way. For reliability, ease of cleaning, and freedom of filter media.