Last Friday I flew on an Airbus A300-600 and a member of the cabin crew asked me not to use the lav on the ground. Being very curious I asked why. He said that the sink leaks on the outside and there are security issues (he further elaborated that they were concerened of hiding a bomb there).
No the question remains why sink and galley wastes leak on the outside and not stored on board to be emptied later
