Where does the water go?

[Oz100]

Perhaps I am confused and got this wrong, please put me right, but when tiling my shower if I use the following steps -

1) Tank walls
2) Use tape or silicone to seal edge of tray to tanked wall (No fins on tray)
3) Use good, shower suitable, adhesive
4) Use good grout (probably BAL)
5) Silicone to seal around bottom of tiles to tray.

Eventually I should expect that even with this setup the tiles and grout will leak through to the tanked wall. Now here is where I am confused. Where does the water go then? I would expect that gravity means it continues migrating down through the adhesive, but when it gets to the silicone, at the bottom, it has nowhere to go....

 

[PrenticeBoyofDerry]

It will either creep back in to the tray via failing grout or if silicone also fails, puddle underneath the tray, if the floor is also tanked. If not, it will start tracking downwards.

 

[Oz100]

Is grout / adhesive which lets water through actually failing?
I have read numerous times, on here, that cement based grouts are not waterproof, that tanking or waterproof board should be behind the tiles and tiles in a shower should not go directly on to plasterboard as it will quite quickly begin to absorb the water that has penetrated the outer layers. Perhaps I have read too many horror stories, but I have got the impression that even a good brand grout is absorbing water in normal circumstances, or have I got the wrong end of the stick?

 

[PrenticeBoyofDerry]

A cementitious grout will absorb water and are best sealed after the have dried.
With regards to the type of surface that tiles should be applied to, I am all for bely/braces methods, but at the end of the day if the tiling is correct and sealed correctly, there should be no issue. I have on many occasions tiled on to standard plasterboards in wet areas, and they have not fallen foul to moisture ingress.