I've had a few instances of the clear EC pipe squashing flat under vacuum ..   It usually happens close to the barbs / connectors as described, but it is easily cured
Just insert some of the infusion spiral inside the tubes .. All my "permanent" vac-lines are done like that .. (from the pump to the catch-pot) and from the catchpot to the "connector" where i connect the "throw-away" piece of tube to the bag connectors.  I never clamp on these pieces of tube .. only close to the bag ..  It has not happened with any of the last batches I've bought from EC ..

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