Mucky grouting in floor tiles

[Dotty342kids]

We moved into our house six months ago. The kitchen is about to be refitted and in doing so I think we're going to expose a few places which we'll need to retile (there is a stack of spare tiles in the shed). However, when they get put down and grouted then it will become very obvious how dirty the grouting is between the existing tiles, as opposed to the new tiles.
Without scraping out and regrouting all the others (it's quite a big kitchen and the flooring also goes out through the hallway), is there a way of cleaning the existing grouting and returning it to the white / pale grey colour it was originally?

Bump

I could do with tips on this too.

My builders cleaned our white grout using very fine sandpaper. Beyond time-consuming but it came up a treat. You can also buy special grout cleaner but it requires a fair amount of scrubbing and results may not be any better than using an abrasive cream cleaner, IMO.

I've found that just putting neat thick bleach on the grout with an old toothbrush, leaving it for 10 mins or so, and then scrubbing at it with the toothbrush, works a treat. All our grout went back to white.

Windows need to be open, children and pets kept out of the way, and the floor thoroughly washed afterwards.

I wonder of a steam mop may do it? don't know because I haven't got one but like you my floor is just to big to deal with it on hands and knees.

The bleach isn't hard work, IYKWIM - just somewhat time consuming.

Neat bleach, if necessary several times (let it dry in between) works on most grouts.

Thanks folks, that sounds like a delightful job........... but if it works!

i use a spray by wizz, mould and mildew
its brilliant for grout, the black stuff that seems to grow in showers
you usually get it in the pound shop. it has to be wizz brand. i have told so many people about and they all cant believe how good it is

sorry, its priced about a pound

I used to work in a hairdressers and we used to mix up hair bleach and put it on the tile grouting - worked wonders!

Special grout cleaner - works but takes a lot of scrubbing.
Cilit bang with bleach is quite good. Scrubbing also needed! But I only do it when I'm in the mood and do sections at a time. then it's quite satisfying in an odd way.

DH bought a hand held steamer thing at Robert Dyas. Which is useless at cleaning upholstery but does also work on the grout, although it is very slow as you have to work along each groove veeeery slowly. I think I'll stick to the scrub method in future.

I made a paste with soda crystals -and used scrubbing brush. As they were abrasive worked very well - you are only really removing the top layer of grout...