You need to remove the connecting oval shaped "tube " that the micro filter attaches to. That tube attaches to the vent hole in the firewall. There's a lever you have to pull toward the front of the car, to release it from said vent hole. Under that tube is a recessed area that has a drain in the front outer corner, about the size of your little finger. When that gets plugged, the water fills up to the vent and pours into the cabin.