I used 4" DWV (PVC Sewer Pipe) for my central dust collection branch lines.  I don't use blast gates.  Instead, I just slip fit a 4" cap over a short piece of pipe extending from a 45 elbow.  These splices slip inside the 4" DWV perfectly for a friction fit.  I leave one of these splices clamped in the end of a flex hose and just plug into the system whenever and wherever I need.  These are too small for the DWV fittings, but they are perfect for the DWV pipe.  Cheap, Simple, and Works like a charm!  (Yes, I'm excited over a hose splice, take your victories when you can!)