After 3 years in a brand new house, I got tired of the constant mould issue in our shower.  The kid's shower was tiled with epoxy grout, but ours with the usual grout (different style showers, different type grout).  The tiler used epoxy grout only on the floors and on the kid's plastic shower liner.  The kids have virtually no mould, but we have lots except on the (epoxy grout) floor.  Used lots of different things, including vinegar which over time etches the grout so makes it worse, and methylated spirits which (over)feeds the mould until it burst and dies but looks ugly.  In a year or two we'll get the tiler back to replace the silicone, will get him to also replace our wall tile grout with epoxy grout.

So this is what I've done yesterday in an attempt to get sanity for a bit longer, wonder what you guys think (and maybe give others ideas for their mould issues).  First I've used a (Karcher handyman's) water blaster to clean out as much as I could.  I though I'd need to be careful, but no issues at all.  Even silicone withstands a brief blast as long as you don't go in under a lifted edge.  You could see the mould wash away, leaving only some (light) black stains.  Wow, it is fun using a water blaster in a shower.  Glad we have a big shower about 1mx2m.

Next was cleaning (bleaching) with Janola spray to make it look better.  This one does not have bleach in it, it has peroxide so is a bit easier to deal with.  Then I've wiped down and dried it out with the assistance of a dehumidifier.  The bathroom was tanked out with a sealer membrane (including the ceiling) so no risk of moisture getting stuck in the framing.

After it was dried, I've applied some water based acrylic sealer.  It is a sample of Holdfast Armacrete that a supplier gave me a few years ago, easy to paint on and then rub excess off with a microfibre cloth.  Decided to also paint over the floor tiles, it might just make them less slippery.

So this morning I've tried the shower, and can say the sealer will make a big difference.  Normally the grout would get a wet look after a minute or so, but this morning it stayed its dry colour so with no water to feed mould, there should be no more mould.  And the floor tiles are less slippery.  It is just short of feeling like a sticky floor, very happy with it.  I might even paint the rest of the bathroom floor.