HCG

Thanks @markc and @ProDave for your input. I think it has internal overflow. I'm going to have to get the whole thing out again so I'll post a photo. The seal above was one of those foam ones and from looking at some of the other questions on this forum, they don't seem to be flavour of the month, so I might need to change that too...

Hi everyone. Does anyone have experience with a silicone washer for the basin waste? When I try to tighten it the nut against it, it just seems to bounce back. Has anyone managed to make this work? Does it seal anyway? Should I just get a rubber one instead? I've searched the internet and can't find reference to such a thing. It's the last bit of a really complicated bathroom job. Many thanks in advance for any advice!