Replaced the lav sink and upon re-installing the PO drain everything seemed to go well and fit well but I found a small drip coming from the sink at the rubber gasket on the underside where drain connects to sink. Looking at the gasket there is an area that had a small gap like it was not sitting tight against the underside.......so, I pullled the drain apart from the since, and reapplied plumbers putty to the drain flange, carefully pushed up the rubber confexed rubber gasket so it met the bottom of the sink bottom and tightened the nut and still see a small crack (the rest of the gasket seems to be tight against the sink . I suspect that the domed part is what helps seal the fitting but do not know since you cannot see in there....could I put a piece of graphite packing on the gasket in the area that seems like it is not hitting the sink base tight so the gasket might lay uniform against the clay bottom.....jor is there something else I might use or you might suggest. Being it is clay and clay is not always that perfect, it does not suprise me that a gasket not lay perfectly flat. I do not want to try and force the gasket anymore and snap the nylon nut.

 

Are your parts for the drain off the old sink? if so the rubber washer may have to be replaced.

If you get a new washer put a little pipe dope compound on the bottom of the drain hole before you install it. With the poor castings of sinks now days they are rarely smooth at the drain hole, you may have to get a metal pop-up so you can get a little extra tightening on it, luck.

BTW if the bottom of the sink is extremely rough you may have to replace the sink.

 

Yes they were off the old sink but faucet was only put in a year ago and I did look and feel the washer carefully and found nothing to suggest is was damaged. I did not know if in fact contractors apply a waterproof adhesive on the bottom of the clay drain opening as standard procedure to compensate for the possible roughness of the clay and if so what they might use.

Appreciate your input, may have to replace the washer if nothing else works.

 

Do not use any adhesive on that drain!!, you will be pulling your hair out if you ever have to take it off. Pipe joint compound is not adhesive.