I currently have a furnace running off natural gas which vents through the roof using PVC. Would it be possible to join a condensing tankless water heater which vents with PVC down stream about 10-15 ft and use a common exhaust.
I would rather have one exhaust vent running through the roof than two.
Both are power vented I believe.
The tankless is 199,000 BTU, not sure about the furnace.