Recently, my bathroom sink stopped draining. Seeing as I am a Do-It-Yourself kind of girl I plunged it and the clear water became gray. The water did start draining very slowly so I let it drain completely. I left the fluffy looking gray sediment in the sink. When I touched it it was kind of filmy. I then removed the U shaped pipe. It was not clogged but there was this black filmy stuff lining the back half of the pipe (the part closest to the wall), but not the part directly under the drain.

I then removed the drain pipe and pulled out the stopper and discovered a bunch of hair and mystery gray gunk all around it. I removed this and went to reassemble the pipes. As I was putting the U shaped pipe back on I noticed black stuff on my hands so I stopped and ran my finger around inside the pipe in the wall under the sink. Can I just say EWWW! I pulled my fingers out with this black sludgey, slimey stuff on them. The nearest thing I can compare the consistency to is bearing grease. (Sorry my dad was a mechanic... not a plumber... alas) It did start draining a lot better after I put it back together, but the bathtub doesn't drain overly well and the toilet doesn't flush well either. The toilet does occasionally overflow, but does respond to flushing in so much as it returns to its normal slowness that never seems to completely flush except on the miraculous rare occasion.

I tried finding info online, but everything kept mentioning well systems and I am on city water. I do know the house was built in the 40's or 50's, but I don't know the exacts because I rent. I guess what I'm really needing to know is if that sludge is dangerous healthwise or just a nuisance and do I need to tell my landlord about it?