Sump return box size?

[Robo_Reefer]

Hi all.

I am making a cube sump. 52(w)x44(L)x40(h)cm. My return pump will be in its own section (as expected). But my question is how large does that section have to be? Currently it is about 18(w)x20(L)x21(h)cm, which is plenty of room for both my pump and a one wall a bubble trap. But it is not a massive area, and I guess I need to have a ATO float in here for my RO water inlet too?

Image link: https://ibb.co/54q0zNw

Thanks a Million!

 

[lapin]

The ato float will go in there.
The chamber needs to be big enough to hold enough water so your return pump does not run dry or produce a vortex.

 

[Robo_Reefer]

Ahh, the vortex, that would likely happen in such a small chamber. Best to avoid that.

Below is a 2nd try. With a bigger out chamber.

I guessed I can put the filter sock in the refugium to save space?