Hi, first off, I apoligise in advance if my terminology is wrong. I recently replaced a faucet and drain in my girlfriends bathroom. Everything was fine, no leaks...except for one.

The new metal drain body slipped easily into the existing black plastic waste water drain, and is in there by approx 3 inches. I used the existing slip joint nut (coloured white) to tighten the connection between the metal drain body and the plastic waste pipe.

When I turn the water on, a very small amount seems to come up the INSIDE of the white slip joint nut and pool around the top edge of the nut and then comes over the lip , hence the leak.

I know these nuts are not to be over tightened, Ive tried undoing and reseating the nut but nothing works. If I put plumbers putty on the threads on the slip joint nut..would that fix it, or is that a bad idea..?

Many thanks in advance....