Replacing grout on bathroom tiles


The grout on our bathroom tiles is mouldy and the old tricks like toothpaste and grout cleaners barely work. We asked a tiler to replace the grout but he said the tiles were too close together and he risked breaking the edges off the tiles.
Please can I have suggestions - do I need to remove the old grout and if so how.
Also, how do you stop the mould coming back?
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I use a good quality thick neat bleach, put on with a soft toothbrush, and leave it on for a few hours before rinsing off, works every time and seems to last for months. I also use that method for cleaning bath sealant successfully. Usual precautions apply regarding testing and checking surrounding surfaces to ascertain if the bleach will affect them, wearing gloves, goggles, mask, respirator and chemical protection suit, and I try and keep the bleach on the part being cleaned as much as possible, but I have had no noticeable problems with the tiles, or the bath, and I have been using this method for several years.
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You can get grout whitener/paint in special applicator tubes - Polycell do it, I think.
Rob Graham
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