Nitrous oxide gas leak when charging ISI whipping cream dispenser When I charge my relatively new ISI cream dispenser, the N2O gas leaks around the top and body seam, resulting in failed whipped cream.  I've tried everything to tighten the seam, including adjusting the gasket and tightening the top very hard.  The demonstration videos show the cook lightly tightening the top and they seem to have no trouble.  What am I doing wrong?
Is it clean? it does not take much pressure to properly seal an iSi. Either it is dirty or it is defective. I have had the issue you describe, the issue was not actually in the gasket around the top of the container, but instead in the gasket around the nozzle. It must be completely clean to hold pressure.