My bathroom sink is plugged solid. I tried to use snake under sink but can't seem to get it in very far. There is an old corroded clean out sticking out of the wall behind the toilet so I removed the toilet to get at it but it doesn't budge. It has a square nut on the top of what looks to be a brass plug in a cast iron pipe? There is a silver soft substance ( I guess a seal?) that I have been picking away since lubricating oil did nothing. Am I wasting my time , should I just go through one on the roof or there is one on the ground outside next to the bathroom, would that be the one I want to try?
If I do need to go through the one in the bathroom how do I get it open??
Please advise ASAP----thanks!