Originally Posted by Bob-D659
Look at photo three in post #18. The hot water heater is an atmospheric gas-fired type that draws combustion air from the room in which it's installed and vents its exhaust via convection through a galvanized steel stove-pipe chimney. As opposed to the space heating furnace, which is a sealed-combustion condensing type, drawing outside air through one PVC pipe and venting its exhaust through a second PVC pipe.
Originally Posted by Steve Smith
Balanced ventilation of the space is definitely necessary to avoid problems with water heater exhaust gas. I still wouldn't do this without installing a fast-acting, low-level carbon monoxide detector. Better yet, partition off the furnace and water heater as suggested in post #9. I'd rather see you go digital than die in a darkroom.