If your cat already uses the litter box regularly, put the litter box over the toilet so the cat is accustomed to where he is suppose to go to the bathroom...after a while, remove the litter box...but drop the litter material as well as the hard litter material with the cat excrements inside the toilet...the cat will still think this is the litter box...this stage is kinda gross...'cause you basically have to spoon out the litter material because it will clog up the toilet if you try to flush it...after a while, you can just not put any litter material inside the toilet...and the cat will just go directly in the water...I have no idea how to teach it to flush though...sorry...

__________________
1995 black pearl/black Mercedes-Benz E420 :