bigfunk

I have the same problem. Black mould spots all the time. I was shopping at the Household goods store at Jurong Point and happen to come across Waterproof adhesive seal strips. $9.90 for 3.2m. And I put it over the spot (between the sink and wall) and no more mould! Saw it at Homefix too but more expensive. Looks something like this. http://www.g4tape.com/index.asp?lbid=628

My common toilet has the same problem, My ID did a check and the smell is coming from my neighbours below. Basically what they did is an illegal modification, so instead of an S-trap it's a straight pipe. I would suggest checking your neighbours piping.