Whitening mosaic grout

[alun02]

Hi,
I've got a mosaic tile floor in my bathroom and it's starting to look a bit grubby, so I was wondering if there's a product available to whiten the grouting? I know you can get a grout whitener but the only ones I've seen are specifically for whitening the narrow gaps between square tiles, and wouldn't be appropriate for the wider gaps I have on my mosaic floor.

Alternatively, is there any reason I couldn't just put a bit more grout down to cover the old grout?

Thanks,
Alun

 

[NickStone]

You could try bleach. If you put new grouting over old, it'll probably flake off.

 

[Moz]

scrape old grout out .....an regrout