Shower leaks & re-grouting advice please

[dr_gn]

All,

Our house was a “self-build” (by me) in 2004. I installed three tiled showers and they have been completely trouble free until recently, when we noticed staining/drips under two of them. I’ve established it’s not the drains; when I tape a plastic sheet over the walls, the leak stops. I put a ceiling access panel under the main one, so I can see directly the drain pipework on that one is dry.

I re-grouted the main shower twice in a matter of months, but the leak persists. Before doing it again - and the other leaking shower, I’d like advice on grout. I did use conventional stuff (which has clearly failed) and was wondering if epoxy grout would finally cure it?

I’m using a multi tool to remove the old grout, and am using silicone sealant around the wall/base joints.

I’ve heard from a few people that once a shower starts leaking, it leaks forever! So any general advice on grout brands, application and clean-up would be much appreciated.

Thanks.