My house was originally built with a centralized wall heater. The previous owner had Central ac/heat installed but ran the chimney to the old exit point in the roof. This means that the chimney has a 10 foot section of pipe that runs nearly horizontal (rises 18 inches). Is this safe?
If unsafe: Can I connect the heater to the water heater chimney that is 18 inches away? If so, I am guessing that I will need to increase the chimney to 6 inches. Is this correct?