Plumbing Issue

[AceRimmer]

Would any plumbers out there know what's wrong with my cold water system?

For some reason, i have a build up of residue on my bathroom cold tap and my toilet supply. It doesn't occur on my kitchen tap or the bath cold tap.

I'm guessing it's something to do with my storage tank as i rarely use my bath tap (I prefer showers). What would be a good solution to clean the system?

[Kos]

Sounds very much like limescale to me. (hard, grey, powdery substance?).
It has built up on your tap through lack of use. There are products that claim to remove it but it is an obstinate so-and-so.

[AceRimmer]

Thanks for you answer Kos, but it'd definitely not lime scale. It's black and slimy not hard and grey. It's on the tap i use most and the toilet.

[gucciman]

im a gas engineer rather than a plumber but your toilet supply and your bath cold tap are both mains fed not tank fed so it cant be the tank causing the problem.

if its black and slimy it sounds like mould.