Our shower is leaking slowly from somewhere, causing the ceiling of the room below to stain. We had the silicone sealant around the edge of the shower professionally replaced and it looks like a good job, but the leak persists.
The shower has no visible tray - it's basically a wet room with the floor tiles extending into the shower area. The room was fitted before we bought the house but I'd estimate it was probably done between 5 and 10 years ago. Some of the grout between the tiles on the shower floor is looking worn and cracked so I decided to regrout the floor in a further attempt to fix the leak.
After removing the metal drain cover and plastic insert, I found a thick layer of grout around the edge of the square plastic drain surround, which was quite flakey and crumbly, so I removed it all.
After doing so, I found a couple of holes between the tiles and the drain surround. Also, with this layer of grout removed, when I put the plastic insert back there is a large gap between it and the edge of the tiles.
My questions are: How should I fill the holes that I've found between the tiles and the drain surround? And how should I fill/seal the gap between the plastic insert and the edge of the tiles, given that the gap varies quite a lot in width and is quite wide wide in places, whatever I do will be visible when the job is finished, and the plastic insert is somewhat flexible when the metal drain cover isn't in place?