I reciently installed a new sink/vanity/faucet/drain in my mother’s home. When I connected the drain, it leaked, but only while water was backed-up from the trap to the sink bowl.The tail-piece I installed was one for a sink with overflow (it had a hole where the overflow enters the tailpiece). There seemed no way to seal the threads below the overflow hole in the tailpiece. I’m sure the leak was around the threads. I replace the original tailpiece (I guess this is also a popup assemble) with a metal one, it also leaked. I tightened the large nut that compresses the large rubber washer very tightly, probably overtight, instructions said hand tight.
Does this make any sense? Is there any way to seal the threads around the large gasket just under the bowl in a popup assemble with a hole for overflow?
Thanks Lots…Ron