Sink leaking

Just installed a kitchen sink.The sink i have has got a pop-up plug hole.
This plug hole is screwed thru the centre and attached to a mating part nder the sink.In between this is a massive rubber washer that sits to the underside of the sink.This is where it is leaking.
I have tightened the screw a little then a lot (not too tight i don't want to crack the sink) and even tryed moving the washer around to get a better seal but still it leaks.
You are only talking of little beads of water appearing on the outside of the washer but i want a perfect seal.
Has anybody had problems.How can i solve it

I am having this same problem at the moment with a bathroom sink.

I tried bedding the waste into silicon before screwing it up and also am wary of cracking the sink (being a bathroom sink it is porcelain). And it still leaks enough to cause a problem.

Jelly you need to smear silicon sealant on the washer.

Adam it depends what type of waste you have, if it is like jellys you need to do the same.

If its the type with a collar that slides over the waste thread and then is tightened with a back nut. You need to smear silicon on the first washer to the basin then assemble it screw the backnut up until you have a small gap between the collar and the nut then wrap heaps of ptfe tape in that gap, then tighten the nut.

By the way the bottom of the collar has a washer too. don't do what most people do and use the washer to try and seal the top end (pretty bit) to the basin. If there is a washer for this it is usually a white foam thing

Basins and wastes don't like each other.

Got the same problem

New sink, new pop up plug

When plug is down no problem

When emptying the sink it looks as though water tracks down through the overflow and then leaks out underneath from the large rubber seal. Have tried sealing with the jelly stuff the plumbers gave us and turning rubber up the other way but it still leaks

Any ideas ?

Well plumbers mate seems to have sorted it (fingers crossed)