I have a reaction chamber where gasses are injected to maintain a certain mixture. The container is sort of like a bell, where the bottom is submerged in water to make a seal.
The issue I have is that when injecting new gas into the chamber the excess has nowhere to go, so the water level is forced downward. I would like to maintain the water level difference inside and outside the chamber of <0.1in.
This rules out most kinds of check valves, because the pressure differential is too low. What I'm currently doing, is intentionally leaving a small hole open in the reaction chamber to allow pressure to equalize. Gas is injected at a very slow rate, so this works ok, but unwanted diffusion is always occurring through the hole.
Does anyone know of a mechanism that will allow the pressure to equalize, but which will not allow significant gas exchange once the pressure is equal? I'm thinking something similar to a water trap, but with even lower pressure drop.