Kitchen sink waste pipe connection leaking.

[robiow]

I have just fitted a washing machine and dishwasher to the sink waste with a new double nozzle trap. But I have a leak at the waste pipe connection. Does the big black rubber washer thingy go deep in the tube (about an inch) or flush with the very edge, plus, do I need to use ptfe tape ? Thank you.

[robiow]

It's o.k folks, sussed it.
I had kinked the rubber washer, which was deep inside tube, still there, but was more careful tightening the ring. I put ptfe tape on it this time aswell.
Thanks for reading this all the same.