I've been working on my central dust collection design for some time. I've read the works of bill pentz and sandor nagyszalanczy as well as many posts on this and other sites. I've decided to play it safe and go with 26g steel ductwork and calculated a 5" main with a few 4" branches. The cost difference between the metal and pvc pipe isn't all that much - maybe $75 in my case.
That said, I'm getting really stuck on the wye connectors that I need to transitions from my horizontal main to The vertical branches that go to the machines from above. At $45 each the total cost of the system is going to get out of control fast. I have a 2hp collector and I'm really not worried about collapsing a cheap wye connector. Can I just use the cheap Home Depot HVAC connectors with my 26g pipes? A hvac wye looks to be less than $10.
Or is this a fools errand and you either go pvc and deal with it's issues or cough up the big bucks for the metal connectors?