I think I'm just about ready to loose it and take the lump hammer to the basin I've just installed....
Fitted a basin two weeks ago and I haven't been able to stop it leaking since (although some days I do just give up completely!!)
First I tried silicon sealant around where the waste outlet enters the basin but it leaked from underneath, I tried bedding the outlet on some plumbers mait and it still leaked, I then tried the silicon again but with PTFE tape around the thread of the outlet and yes it still leaked..even tried plumers mait/PTFE with no joy.
Yesterday I replaced the washers as by now they were gunked in plumbers mait and silicon! I assembled the waste outlet with just the rubber washer (no silicon or anything) and some PTFE tape on the thread and it appeared to work..execept the basin didn't hold water, water was running down into the overflow slot and out into the trap, then I tried it with hot water and guess what..it poured everywhere and I'm back to square one.
I'm putting the rubber washer over the waste outlet, popping it into the hole in the basin, then underneath I'm slipping the plastic washer onto the thread and tightening the back nut up as tight as I can by hand.
What am I doing wrong? Is it possible to get a 'faulty' waste outlet that's out of shape or something? I feel like I've tried everything and the only thing left is the lump hammer which is coming out on Saturday if it doesn't stop leaking!!!
Cheers