So as to not hijack other threads I wish to ask a question. Everyone seems to believe that plastic is cheaper to install than metal. However I don't believe I have ever seen anyone post the actual numbers. Has anyone really run the calculation?
Here would be my assumptions for a garage shop system. Trying to keep it simple so it isn't a major effort to calculate. If you have already run the numbers for your system post these instead.
40 feet of straight pipe either snap-lock 6" metal 26 guage from the BORG or 6" green plastic pipe.
Fittings to make 8 90 degree turns in the 6 inch pipe, either long radius metal or using 2 45 degree plastic and a small piece of straight.
3 Wye fittings
Hangers as needed say 10.
Primer/Glue for plastic, or metal tape for metal.
I am going to ignore the cost of adapters from 6 to 4 inch pipe, blast gates, etc. since this could be interchangeable.