My drains are not plugged, I have done major plumbing in the past, have all the right snakes and cleaners and removed the P Trap and it was clear. The Clam-shell sink has been like this since new, the built-in lever plug appears not to lift high enough (even after adjusting) and the water just *creeps* out. The vent hole isn't plugged, and only that sink has the problem. The P Trap is 1.25" Plastic pipe, no clogs, nothing in drain. It is like a manfacturing defect in this type of sink, that they don't seem to *breath* correctly, and are slow to drain because of it.
Anyone have any similar problems? Or better yet, a solution? I wanted to remove the tapset and replace it with one that takes a real drain plug, not the all-in-one lever type. They always give me grief.

The drain plug (inside the sink) should be about 1/4" up. That can be corrected by adjusting the pull rod. If you are still experiencing same problem than I would suggest you remove entire drain from P-Trap and reinstall it. Here, make sure the drain flange (part visible from inside the sink ) is screwed into the drain all the way.

I'm going to play with that adjustment again. I wanted to take the plug off completely, and go to a rubber one to see if that works, but this was a *look* that you pay for when you install a new fancy sink, disconnecting was a *last resort*, my better half might object ;-)
Will try checking that drain assembly again, and let you know if I get satisfaction

Thanks

But on further messing with it, I discovered the gasket is sticking (rubber seal at bottom of levered plug), kind of like it was pinched on installation (or from the packaging), which makes it oblonged and part has shaped into the drain, so instead of being round, it is almost oval. I will get a new gasket when the hardware stores open up again after Christmas. If I pull it up manually (the rubber) and break the stick seal, it works fine. But if you close the plug lever again, it sticks again. If the new seal doesn't fix this, I will be back to continue the discussion..
Thanks all
Merry Christmas!