I was recently doing some plunging in my bathroom (both the sink and bathtub drains.) Suddenly, a little black sludge came up the sink drain, and when I rinsed the basin, my bathtub drain started backing up with all kinds of black gook. Obviously the two use the same pipes. I did some more plunging of the bathtub drain and more gook came up.
I just poured a load of Pequa down both drains. If that doesn't work, is there any more powerful stuff. My friend told me about some black liquid that's in a clear bottle, and a bag is over it. He's not sure of the name of it.
By the way, how much does a drain "snake" cost? I'd rather do it than the super (it's an apartment building) as he leaves a tremendous mess.