Advice On The Finer Detail Please

[Qwerty]

definitely not Silicon. not ever. sub-tile water cannot drain if you Silicon around the gully.

Not even if you used epoxy grout on the former?

 

[One Day]

Not even if you used epoxy grout on the former?

you could argue that in using epoxy you'll be waterproofing the whole thing anyway, but if you really trust that then why waterproof the substrates? the main reason is that Silicon tends to completely fill the area around the drain collar. most manufacturers won't entertain any claims if silicones been used. then again, do they ever?!