A PVC flue is a plastic exhaust pipe made from polyvinyl chloride used to vent low-temperature combustion gases from high-efficiency furnaces and boilers where exhaust temperatures remain below 140 degrees Fahrenheit. PVC flues are lightweight, corrosion-resistant, and easy to install compared to metal alternatives. They are permitted only when exhaust temperatures are consistently below manufacturers’ specifications.
Temperature and Performance Specifications
PVC flues are rated for continuous operation at exhaust temperatures not exceeding 120 to 140 degrees Fahrenheit, depending on pipe grade. Condensate naturally forms as gases cool, draining into traps designed to prevent water from entering the furnace. Schedule 40 and Schedule 80 PVC pipes are most common, with Schedule 80 providing greater durability.
Installation and Safety
PVC flues require proper slope and support to manage condensate drainage effectively. They are typically paired with PVC intake pipes in direct vent or concentric configurations. Installation must include sediment traps and condensate drains routed to appropriate drainage systems. PVC flues cannot be used with appliances exceeding stated temperature limits and are incompatible with furnaces burning solid fuels.