I can't figure out if I have a unique and good idea or if I just missed the bus. My guess is I missed the bus a long time ago, but that won't stop me from throwing this nugget out there. I finally replaced the mercury bubblers in my research lab. It was time. I have had people say they use oil bubblers. I tried that for about a day and really hated the lack of pressure that I was so accustom to. I had to find another solution. That's when I found Inert Relief Valves (20 PSI) from Cole-Palmer. I am sure there are others out there, and I get no money from Cole-Palmer, they just happen to be the one I found. Anyway, the valve has a threaded input and output that pretty easily can be set for standard tubing sizes. There is a set screw that controls the pressure at which the valve will open. I have found opening the screw almost all the way and then setting it in place with a glue gun works well. On the outlet I hook up a normal oil bubbler. It will bubble pretty fast when the line is in operation, but you do get a bit of a pressure boost without the Hg. I have been using these for about a year and they seem to hold up pretty well. And they aren't too expensive ($64).