Originally Posted by
Lovecruising
Personally I wouldn't want to sit on a toilet where someone had done their business and it was still there. The toilet couldn't flush due to no water.
That's the difference between flush toilets - which use up to 5 litres of water to deal with 300ml of waste product, and gravity-suction which uses less than 100ml (and mainly the swill some cosmetics around). And as suggested, you cannot in practical terms use flush toilets on an aircraft.