How to Clean Out a Blocked Furnace Downdraft Pipe

A downdraft, or downflow, furnace work similarly to an updraft furnace with one major exception. The fresh air flows into the furnace from the top, or downward, and the heated air comes from the bottom vents. This is the reverse of many furnaces. The downdraft vent pipe on the roof that allows fresh air to enter from the outside can become blocked, so it's wise to check it before the cold season starts.

Flashlight
Screwdriver
Wire coat hanger
Wire cutter
Cord
Packaging tape

Instructions

- 1
  Inspect the downdraft vent pipe where it protrudes from the roof. The vent will be directly over your furnace. If the cap is on solid with a fine mesh screen, blockage may not have occurred.
- 2
  Remove the cap if it's been damaged or torn. Vent caps usually just screw onto the metal stack.
- 3
  Look into the stack with a flashlight. Any bird or insect nest obstruction will be in the first few inches and easily visible.
- 4
  Bend the coat hanger into a broad hook shape with a long handle, if you see an obstruction. Cut off any unnecessary portion of the metal. Wrap the cord around the end of the coat hanger and secure it so the wire won't slip and fall into the vent. Wrap sticky tape around the hook portion.
- 5
  Reach into the vent with the hanger and pull out any debris you find. A wasp nest may have to be sprayed first with wasp killer to prevent stings. Continue to remove the debris until the obstruction is clear.

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