My 20# CO2 cylinder is finally running out. It's dropped to 500 psi so all the liquid is gone and it's running on the compressed gas. However I noticed a large increase in the bubble counter at the start of today's 8 hr run. I have the pressure set to 60 kPa so I could have more needle valve control adjustment range. Well today it was just over 100 kPa and bubbling like crazy. So I bumped it to a much higher 30 psi and readjusted the bubble counter. I'm thinking a small ~40 kPa change of pressure at 30 psi won't be as big a deal as it was at the very bottom of the regulator's pressure control range I was running at.