Straw filter type filter outlet

[Clulu1]

Hello !

I am looking for an idea to design a sort of "homemade" straw filter adapted to the configuration of my drainage system .... indeed the outlet of my gray water sink / shower arrives in a manhole. ground level, from which a larger pipe starts again, that of the evacuation. I would like to filter in the manhole, but the concern is that my two pipes will be almost at the same level, so I cannot install a filter straw since the filtered water does not come out at the bottom but almost at the top of the manhole. Hope this is clear enough! Do you have an idea of ​​how I can filter the residues between the small and the large hose (especially those of soap which tend to clog the pipes and grease for the kitchen quite quickly)?
Thanks for your ideas !

[GuyGadeboisTheBack]

A small photo, maybe?

[Clulu1]

Hello !
So photo no because the house does not yet have its network, we are in the process of designing it on paper ... but here is a diagram of our situation for the bathroom:
The interior ground level (red dot) is higher than the exterior ground level, so the pipeline is already exiting underground.
We will have to place a drain along the exterior wall with stones and backfill, which will bring up the exterior soil. Basically, the pipe entering the manhole will end up at about 25cm below the level of the final exterior ground.
This is where I would like to be able to install a straw filter system or other on the principle of a grease trap, in order to retain soap residue and other possible bathroom residues.
You understand that I am a bit limited in terms of depth.
On the other hand, I will also apply this system for the kitchen and washing machine drains which will be on the other side of the house ...
Finally, when I see that the recommended volumes of grease trap for gray water are 200l to 500l, I wonder if it is not ridiculous to want to install a simple straw filter system

Anyway, thank you for your help!

NB: ignore the drawing of the pipe in red