[Closed] Plumbers / Bathroom Fitters: Quick question

I am not a plumber or bathroom fitter but a management accountant/CFO for a proprty company. I have become the accidental technical manager who solves issues like this, and have had certain plumbers tell me these do not need sealing, but when the shower leaks into the room below we often find these are the source.
So yes a seal is needed, otherwise it will leak behind, I have seen some where it is pissing in through the gap at the back. In our residential and commercial rented properties I always spec silicone underneath, eg that round plate - they will put a bead between the silicone and the wall and when it compresses they tidy up any squeezed out. If they get it right , then very little squeezes out.
This is the associated issue with wall mounted stuff like this that people often overlook, when you re-do the tile to bath/shower seal you often have to do these too.

Probably, yes.
Some have a rubber seal behind them, but if the tiles are not perfectly flat, water will leak behind the cover even with a rubber seal.
I'd be getting the clear silicone out.
Dow Corning 785 is one of the better silicones.

There should be a seal of some sort between the surface and where the pipes go thru the wall. sometimes there is a rubber gasket, sometimes there is the silicone hidden behind the cover, sometimes a visible bead of silicone.

sounds very much like you have no seal at all on some of the fittings. The second one to my untrained eye looks like it could well have a hidden rubber gasket but with the small tiles it will not seal fully as water can still get down the grout lines.

Of the three fittings over my bath 2 have no visible seal and one has a visible bead of silicone. all 3 are actually sealed tho very carefully by me

You need to take the plate off it and see what's going on behind. When my bathroom was done I queried why the shower controls didn't have sealant against the tiles, the plumber showed me the manufacturer instructions that it shouldn't be sealed and all the sealing was done where the pipes going into the wall (which he showed me).

Probably needs sealing due to the uneven nature of the tiles.

I'd look for a sealant suitable for use on stone though as those look like a natural stone to me.

You might also need to seal them as I suspect they are a very porous tile, and with big grout joins even more chance of water penetration.

Installed in the centre of a large tile, no probably not.
On those tiles, almost certainly.

Difficult to say for sure though without knowing what's going on behind.

as fuzzywuzzy, all the sealant on my pipes / controls etc is under the plate where the pipes / controller innards come thru the tiling, so take the cover plates off and see what's been done underneath.
Also as bear / nealglover, those tumbled travertine tiles are very porous and with lots of grouting ie small tiles, possibly the worst choice the previous owner could have made. maybe try resealing the tiles /grout. the other question is what's under the tiles, did they do a proper sealed membrane job?.

The plates are not easy to get a good seal onto, which says to me that they're not intended to be sealed. I seal the pipes into the wall and assumed the plates are just there to make it look good. On replacing one shower, however, the pipes were too deep in the wall and I could only fit the plates if I cut a holes in the tiles, so I did seal them. But the hot pipe expands when the shower is in use and stresses the seal.

Thanks for the advice.  The plumbing in the other bathrooms is less than stellar according to the plumbers we had in for those so I'm not holding out much hope for what's behind the plates. Those little tiles are a nightmare which is why we avoided using that shower initially.