The outlet to the drain is actually on the side of this waste fitting - I know as I have exactly the same type in my shower, so you won't find it easy to stick anything down like wire coathanger etc.
How long have you left the sink unblocker chemicals down there for? I find it needs about 4 hrs to get to work then I flush with hot water using the shower hose directed into the waste (no good if you have a fixed head shower of course). My shower is pumped so plenty of pressure there.
Alternatively you could flush with a hosepipe - I find it needs that full force to clear the muck. You may also need to plunge but definitely do it wet. With the drain full of water the hydraulic pressure will help to clear it.
kbdiy : do you know the style of plug and waste we both have for this shower?
If I could then see a google diagram of how its working (below) I could maybe get my head around it better, as I have a limited view from above!
Yes it will do. The problem as I see it, is that the 'tube inside a tube' design doesn't allow for much force under normal flow conditions, so the likelihood of a build-up of muck is higher as the outlet flow doesn't have a direct 'push' from the water above (makes sense to me anyway!).
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