Reverse sink overflow

Yesterday’s home hand 2 cultured marble bath sinks with the overflow drain manually plugged. There are flow stains running down to the drain. I can come up with no scenerio to explain this. (Even a back-up problem should flow out of the main drain until the overfolw level is reached, right?) Has anyone dealt with something like this? Thanks in advance.

Cluless in Oregon :shock:



Plunging the sink while there are chemicals such as drain cleaners can casue staining in those types of sinks if there is a lot of gunk in the overflow. It gets chemically etched into the surface of the sink.

Ding,Ding,Ding,Ding. Thank you Scott, my melon didn’t go there. (79 others didn’t either.) Thanks again, that is the only logical explanation, for the manual plugging also, not enough force with open o-flow.:):):):slight_smile: