What is the proper pitch for the flue pipe when installing a category IV condensing furnace?

The proper pitch for the flue pipe when installing a category IV condensing furnace is 1/4 inch per foot. This specific pitch is recommended to ensure that any condensed water vapor created during the combustion process properly drains back to the furnace rather than pooling in the flue pipe. Category IV furnaces are designed to vent extremely low-temperature exhaust gases, which can condense and produce moisture. A slope of 1/4 inch for every foot of pipe helps to facilitate the flow of condensate, mitigating the risk of blockage and potential damage to the venting system. Proper installation according to manufacturer's guidelines and industry standards is crucial for efficiency and safety in the operation of the furnace.