1. The problem statement, all variables and given/known data I am attempting to collect bubbles that are being produced under the water surface. The bubbles are natural gas, lighter than air I can collect the by bubbles by directing them into a funnel and up a hose and into an airtight collection vessel. I want to know what pressure is required before the air in the pipes and vessel will be expelled back out the funnel, through the water and back to the air. Mouth of the funnel is several centimetres under the surface of the water. Can anyone think of a better way of doing this without pumps etc.