Installing ventilation conduit into larger ventilation conduit
We used to have a gas water heater (4 inch exhaust conduit) and a gas furnace (5 inch ventilation conduit) that both fed into a 8 inch main ventilation conduit that runs from our basement up to exhaust on the roof on the second floor. The gas furnace was just replaced with a new, high-efficiency furnace that required a new exhaust line to be run. So now, only the gas water heater (4 inch exhaust conduit) runs into the main 8 inch exhaust conduit. I would like to install a new ventilation fan in the basement but avoid punching another hole in the back wall. Is it possible (not just physically but legally) to run a separate, sealed powered vent exhaust line (4 inch?) up through the existing 8 inch main exhaust conduit? (no co-mingling of natural draw water heater exhaust with powered vent exhaust) Thank you.
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