Shower wall grout is still leaking after regrouting - Please Help!

Hi all,
Just bought a house that was "refurbished" by the previous owner. I think she did all the work herself, or with the help of a builder friend. Unfortunately, now it's my responsibility to fix bits of it up that weren't done properly. After a couple of weeks I started to notice that the shower wall tiles, after a long-ish shower, were showing grey watermarks that started from the grout line and headed toward the centre of the tile. Tiles are white by the way. The watermarks varied in size from about thumbprint size to around double that.
I've Googled for hours and been reading this newsgroup for the last 2 or 3 hours as well and am still not 100% sure how to proceed. And, I should own up at this point, I've already removed ALL the grout (not the caulk) in the shower and done it over once, including using a paint-on sealer on the new grout a couple of days after the grout was installed (?) - which didn't improve the problem!
It IS possible that I screwed up the mixing process for the (unsanded) grout and made it too hard - it ended up sort of like putty and I was told it should have been more like toothpaste.
My question is this: Should I attempt to do the job again, assuming I can do a better job mixing the grout, or is there a bigger problem?
I'm not a home-handyman by any stretch of the imagination, but as this is my first house I wanted to have a go at fixing a problem myself. I haven't seen any other post about re-tiling or re-grouting that mentions watermarks (darkened areas) on the tiles themselves, only the grout lines. I think the tiles are reasonably new, within the last 6 months or so. The watermarks disappear after a few hours, but I still worry that it can't be good for them to be appearing in the first place.
I haven't called a professional because, just having bought the house, money is still a bit tight.
All advice appreciated.
Cheers, Ben.
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Ceramic tiles are covered with a glaze which basically is a coating of glass like material that is melted onto the tiles in a kiln. Nothing should cause the surface to have "watermarks" on the glaze as it is impervious to liquids or anything that can soak into the surface.
However, if the tiles are thin and porous as some real cheap tiles are, you possibly have a water problem behind the tiles. If they were not installed properly, possibly not using a water proof backing, there could be water penetrating the grout lines, especially if they were not done right. This water could be soaking into the tiles from behind and showing up as wet marks behind the glaze. As the water evaporates or is absorbed uniformly throughout the tile or into the backerboard the wet marks will dissappear.
I don't think anything will cure this other than a total tear down and replacement with cement backerboard, waterproof membrane, thinset mortar, good quality tiles and a good grout. You may find a lot of mold growing in the wet environment behind your tiles.

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Most likely the tiles are cheap, used glue to place tiles on green board and a crappy grout job.
Its a total redo.
Use Cement board. Use Thinset Use a Good tile
Use a professional

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Tile should not absorb water. These must be some wierd tile.
Did you seal the grout after you re-did it. If not, that might help, but probably won't.
Grout is not waterproof. If the tile is permeable, the grout can't stop it. Epoxy grout might, but that's not sure, and it is more involved than regular grout.
Bob
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alone, then the tile will absorb water. I have seen some of this junk, it is thin, soft and porous, made in some third world country to no standards. Certainly not hard pressed like the good stuff. Rip it down.
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Thanks for the responses guys. I'm in Australia, don't know if that makes any difference to the tile sourcing debate.
I did try to seal the grout after a couple of days, but I recently saw another post about the fact that sealing on a vertical surface doesn't necessarily work that well.
I assumed that the leakage was occurring along the sides of the tiles, where the grout and the tiles meet. Even when I laid the grout, the moisture from the mixture caused this same darkening effect on all the tiles. The tiles are ceramic on top but I seem to remember they looked kind of terracotta-ish along the sides?? Does that sound normal? Also, the same tiles have been used to do the whole room, not just the shower cubicle itself. Actually, the same tiles are used in the main bathroom on every wall, including the shower.
I just wanted to reiterate that I believe the water is getting into the tile along the side, not from the back, as the darkening (watermarking) only appears along the tile edges next to and touching the grout lines.
Cheers, Ben. (with heart in mouth)
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After reading your last post, it sounds to me like perhaps the coating/ finish on the tiles is not as thick (or even existent) on the outer edges of the tiles. Sort of like a clay flower pot that gets darker when wet because the surface is porous enough to hold a little moisture.
Have you considered taking a picture of the watermarks and taking it to a tile shop? Not the tile section of a home center, but a store that deals exclusively with tile.
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I've taken a picture of the watermarking but hadn't thought of taking it to a tile shop. Thanks for the suggestion - I'll give it a try.
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