I am considering running emt(galvanized steel electrical conduit) in a concrete slab for the venting, maybe 20 runs or so-thats how the math works out- to equal the area of a 6" flue pipe. 16 runs of 1.5 inch is the same area as the 6" and I would add a few extra because there is more friction/resistance in smaller diameter piping. At the end of the run the emt would run back into a 6" vent and head up and out.
I poked around the archives but didnt come across anything with the same design. Could someone point me to a thread if I missed it, or if this is the first looking at running the venting in a 3.4/4" slab, any feedback would be appreciated.