I have two sinks which are part of the countertop (single unit/casting). One sink is perfect. The other has never had a working overflow. I thought it was clogged but it appears that the overflow hole was not cast properly. I can see where it stops and it looks like the ceramic the sink is cast from.
Is this a problem that I can solve without replacing the sink?
My next step is to take the drain out and see if the overflow cast underneath the sink goes through to the vicinity of the overflow inlet or not.