Cleaning old tile grout

On 10 Mar 2014, Biggles@flies_undone.com grunted:

As per another recent thread, I've used HG Mould Killer successfully to eradicate mould on the silicone sealant in a shower; we also used it on the tile grouting and it was absolutely top-notch at cleaning that too. Although some of the stain on the grouting was mildew/mould, mostly it was that brown residue which you often find on grout.

Thoroughly reccommended.

Thanks, I'll give it a go. Some of the grout has gone orange/brown but most of it just looks dull.

In article , Lobster scribeth thus

I tried some of this and it does "work" but didn't shift a really badly ingrained patch on a rental house undergoing some refurb but the best way to deal with browned off grout is to scrape a little out and put a bit more back in, looks like new;)

Much less elbow grease required too;))..

Bleach works if the staining's light to medium. If its worse, the only real solution is to abrade the surface of the grout off. A grout removing tool works.

NT

I tried bleach, HG mould killer and viakal but without success so bit the bullet and spent a happy (?) few hours today raking-out all the grout down to a couple of millimetres, ready for a re-grout. Thanks to everyone for their suggestions.