Hi,
After re-sealing my bathtub with silicon sealant due to a couple of leaks, I sprayed water around the bathtub to check the seal was water-tight. It was, but I discovered that the grout (I think it's called) above one of the bottom-row tiles had begun decaying and when sprayed upon, water is visible streaming out from the underside of my bath, presumably through the crumbled grout above the tile and down behind the tile.
I don't think the re-sealing is related to the leaky tile (maybe I'm wrong though), as when I was replacing the sealant I noticed that the bottom of this tile appeared to jut out a little more than the others did. Upon closer inspection, I now see that it seems to have moved a couple of millimetres downwards/outwards.
I was thinking about just using a fine line of silicon sealant around the tile to stop the leak, but as the tile appears to have started moving, is it inevitable that it will fall off at some point? And if so, is it fairly straight forward to remove a tile and replace it?