Bypass HVAC duct under slab with DWV piping

[Ntcarson]

Hello - I'm replacing and rerouting some 60+ year old cast iron DWV piping under a slab. I need to perpendicularly bypass the under slab HVAC duct shown in the picture. I haven't punched it open yet, but I believe it to be a 6" duct insulated and encased to withstand the environment. I need to run a 3" drain pipe through the trench shown. I'm coming up with a few ideas, but wonder if someone with experience may have a simple/standard way to doing this. Thanks for suggestions!

 

[Fitter30]

As for as the duct my last house the basement under the main house and family room and garage a slab. Duct was rotted out replaced it with 10" sch40 pvc with the transition was at the foundation wall. Two vents feeding the family room used the sheet metal from old duct to registers. Then ran electric self regulated radiate heat cable and tiled over it. Rented eletric jack hammer for the concrete worked ok with a shop vac running and room seal off with.

 

[Sponsor]

 

[Ntcarson]

As for as the duct my last house the basement under the main house and family room and garage a slab. Duct was rotted out replaced it with 10" sch40 pvc with the transition was at the foundation wall. Two vents feeding the family room used the sheet metal from old duct to registers. Then ran electric self regulated radiate heat cable and tiled over it. Rented eletric jack hammer for the concrete worked ok with a shop vac running and room seal off with.

Interesting - I hadn't considered PVC options! I just figured out that it is 10" supply duct at that point, so a couple 10" pvc adapters might rack the cost up super quick, but I like having that option. Thanks!

 

[Fitter30]

Interesting - I hadn't considered PVC options! I just figured out that it is 10" supply duct at that point, so a couple 10" pvc adapters might rack the cost up super quick, but I like having that option. Thanks!

What would it cost for a sheetmetal shop make duct out of stainless? Measure the duct, figure sq. inches to compare. Pvc is forever plus it's not going to sweat and ground moisture won't bother it. Mine was 12' long all used a pvc cap for the end.