Hi. I have a stainless sink with another small sink next to it. The smaller sink has an overflow into the main sink, it's a plastic bendy pipe. I noticed a bad smell coming from sink, and realised this pipe was full of gunk. In my wisdom, I removed the pipe and cleaned it out. I now have a spare o ring in my hand having reconnected everything. The o ring doesn't seem to fit in the connector to the main sink. Can anyone tell me where the bloody hell it goes? There doesn't seem to be any obvious leak - yet. Thanks