Those products are inherently flawed as even if they worked, once the drain is already clogged it’s too late. Pouring it down the sink doesn’t do much. What ever little of it reaches the actual blockage has already been dilluted so much it’ll probably do nothing. Conversely, when it’s still draining a bit, the chemicals just flow down the drain instead of doing their job.

I have a corner in my kitchen that I can’t vacuum because a spider’s living there and has built a web. There’s even a pile of silverfish carcasses right there, so it’s not like he’s slacking on household upkeep either.

The material doesn’t really matter there - that’s what the waterproofing membrane is for. My bathroom has a plywood subfloor with a 5 cm concrete slab cast on top, floor heating cables embedded inside it. Then there’s a waterproofing membrane painted over that, followed by the tiles. There’s even this rubber “funnel” over the floor drain that’s fully embedded in the waterproofing layer, making it virtually impossible for water to go anywhere but down the drain.

Why shower tray instead of floor drain?