I have just replaced the siphon on my old toilet as the insides had torn and i have had to cut the bottom of the siphon as out of the bottom of it there was an extra piece that went on the bottom with a black rubber that blocked a hole in the base of the pan but now i have put it back together it does not flush as well as it used to and it struggles to take just paper away,, any ideas or help to point me in the right direction