Anna Kettle wrote:

The floor will be made of cement slabs which are cemented together to
provide a fall towards the centre

Below the floor level in the centre I will put a trough which will
catch mortar from the slurry which I sweep towards it and allows the
water to overflow. At the end of each session I will empty the trough
of solids

The trough will need to be resistant to UV and being bashed around and
should have an overflow vent near the top. An old ceramic sink maybe

I presume the intention is to allow the solid matter to settle out
before sending the water to the drain?

I would have thought it would need to hold the slurry for a while to
allow it to settle, rather than having a continous flow through it.
Having a drain at a fixed place may also prove trickey since it will
only work when full - but the level of solids in the tank may be much
lower. Perhaps you need some form of sliding side so that you can set
the level that water is drawn off?

--
Cheers,

John.

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