How to Replace a Furnace Draft Vent

Shut down the power to the furnace. Allow time for furnace housing to cool.

Draw a diagram of how the connecting hoses and wires attach to the furnace inducer assembly. The furnace vent pipe sits on the return-and-supply vent side of the furnace cabinet. Mark each hose and wire according to the diagram using masking tape labels.

Unhook hoses and wiring. Furnace assemblies with wire-socket connections may require a socket wrench to remove wiring. High-efficiency furnaces may also have a condensate drain tube, which requires unhooking. The drain tube sits beneath the draft vent pipe housing.

Disconnect the vent pipe from the furnace housing. On some models, this may require removing clamps and a rubber sleeve, so keep a screwdriver on hand. The end of the vent pipe can either run up the furnace chimney or out through an exterior wall opening.

Reconnect the wires and hoses using the diagram and labels. Reattach the condensate drain pipe on high-efficiency models.

Attach replacement vent pipe. The length of the pipe depends on the distance from the vent housing and the chimney or exterior wall outlet. Replace the clamp and rubber-sleeve assembly. Make sure the clamp fits tightly around the rubber sleeve and vent.

Install elbow joints at bended points along the vent pipe, so more than one pipe segment may be required. Pipe segments slide into the ends of the elbow joint. Secure elbows using four sheet-metal screws at even spacings around the pipe.

Seal elbow and PVC pipe joints with a bead of silicone caulk so that the pipe connection and pipe seams are completely covered. Seal elbow and metal pipe joints with solvent cement. Let it dry.

Restore power to the furnace. Check to make sure vent pipe operates correctly by watching as the furnace runs through an on-and-off cycle. Air should discharge through the vent pipe on the exterior of the home.