To fit the pipe or for the post evacuation wash up?
To be clear, the hose connection for the primers loosens around the same time as it gets full (imho) as often does the red end cap. At this point, just as my brain registers a need to empty out that tube, the bluddy thing evacuates itself all over the floor. Primers being greasy sooty things make a helluva mess. And a piercing wail/ gnashing sort of sound from my betrothed.