Bathroom Washbasin Black Sludge

[dantodan]

Our wash basin often is slow to empty (well a bit). I probe the drain outlet with a stiff wire and get black sludge. There sometimes is the same sludge in the mixer tap!! Ugh! . I dont shave there anymore having switched to an electric shaver. We have tried vinegar, salt, bi carb, soda crystals and various drain unblockers but after a better performance for a couple of days it goes back to slow emptying. The bathroom was new 3 years ago but the pipework will date back to 1971

Has anyone any ideas

 

[Silentrunning]

Take the p-trap off and give that a good cleaning. Before replacing it remove the drain plug and give the down pipe a good brush out. I have found that toothpaste is a great contributor to drain problems.