Wow, thanks for the fast response . I got it working. The additional oxygen pressure in the column was the key.

Here's one way to do it: https://imgur.com/a/bSpQRJO

Good luck :)

I'm finding this challenging to build even in sandbox! I've stacked O2 over CO2 in the bottom left, but every time I remove tiles above the waterfall stops. I'm able to build the Escher waterfalls across vents, but this one is eluding me - any hints?

Perpetual motion at display. This particular design is usually referred to as an Escher waterfall, and is a paradoxical self-powered waterfall. In Oxygen Not Included, it typically consists of a waterfall and a gas based liquid pump.

For more information on Escher waterfalls and other oddities, go check out the Compendium of Amazing Designs: https://steamcommunity.com/sharedfiles/filedetails/?id=2154398396