I have tried baking soda and vinegar and it does not seem to help a slow draining lavatory. I replaced the p-trap and found a lot of black sludge lining the pipes. What about a cup or two of clorine bleach?

Not likely. Better off with very hot water. Get a ZIP IT at HD or Lowe's and try working down the drain opening, typically pull out lots of hair and gunk.

Hi Jed

Pure chlorine bleach will only corrode any metal parts and is bad for your brain cells as well... so steer clear of that, OK? Diluted bleach won't really do much either... read on.

How about running water when you had the Ptrap off... did you try that and if so, was the sink still slow to drain? If so, then you want to pull the pop-up of the sink drain up and out of the sink and clean it real well (or try the "zip it" mentioned by Ma0641). Here, loosen the retainer nut (see image) and pull the rod out of the drain assembly to allow you to remove the pop-up and clean it. Reassemble hand tight plus 1/2 turn and you should be all set.

Otherwise, I suggest you get a hand-held snake and snake the drain... only real solution to clearing a drain for the long term!

Mark