I just watched skye storme's hydrogen bubbler on this https://www.youtube.com/watch?v=v4sKlv081To&t=2560s and I must say I am pretty disappointed In real life, the hydrogen will quickly stop flowing once the pump is switched off and the gas/liquid inside the pipe reaches equilibrium.
Gases and liquids in pipes shouldn't behave any differently from gases and liquids in an enclosed space outside the pipes albeit in a much longer and smaller enclosed space. Water should still flow downhill. Poo water aka sewerage should still flow downhill. We don't need a pump. That's how it works in real life and in-game (when not in pipes), I don't see why gases and liquids should behave any differently just because they are in a different vessel call pipes rather than say two row of tiles that encloses said gases or liquids.
Steps to Reproduce
Follow Skye's design on the youtube link provided
This issue has not been confirmed by a developer yet.