I am having a real problem fitting a new waste to a new small basin.The waste is the one with a slot in the side for the overflow.Problem is try as I might it leaks. I have fitted it with plumbers mate under the plug hole end and then between the rubber washer and the sink underneath so the large nut squeezes the putty into the gap.In fact I have remade this about 6 times so far and it either drips when empying or trickles when overflow tested.
What am I doing wrong?
I tried the washers given with the waste which were a flimsy white one for the top and a sturdy black one for the bottom and they didnt work so the supplier said use pumber mate instead.
Any suggestions gratefully received.