How to Vent Oil Furnaces

Look inside the chimney firebox with a flashlight to locate the flue.

Remove the cover that is on the flue. Generally, it is a metal piece attached with screws. Use a screwdriver to remove it.

Measure the diameter of the flue and the distance from the flue to the oil furnace. Take these measurements with you to obtain galvanized steel vent pipes that are the same diameter as the flue. The amount of piping you need depends on the distance from the furnace. An elbow pipe is also necessary to create an L-shaped connection down from the flue to the other pipes.

Attach the elbow pipe to the flue opening by using an electric screwdriver to add holes and screws.

Seal the flue and elbow pipe where it meets with high temperature silicone and a small trowel. Allow the high temperature silicone to dry according to the package directions -- typically 20 to 60 minutes.

Attach the other pipes together to form the length necessary to reach the oil furnace. Connect them with screws and high temperature silicone using the same method as the elbow pipe. Wait for the silicone to cure before adding the pipes.

Connect the remaining pipes with the elbow pipe and attach it to the oil furnace as well with silicone and screws. Wait approximately 12 to 24 hours before using the oil furnace to ensure the silicone has cured.