How to Clean a Dryer Vent from the Dryer to the Outside Cap

The lint trap catches most of the lint; the rest travels down the duct and collects in every bend and low spot until the dryer is blowing through a felt sock. That is when clothes take two cycles, the top of the dryer gets hot, and, in the worst case, the lint ignites. The NFPA estimates about 13,820 home fires a year involve clothes dryers or washing machines, and failure to clean is the leading factor. Cleaning the vent is a one-hour job with a brush kit, and it also cuts drying time and the electric bill.

This guide covers the warning signs, the tools, the gas-dryer cautions that matter, the full cleaning from the dryer's exhaust port to the outside cap, the transition duct you should probably replace while you are back there, and when the job belongs to a pro. Our maintenance calendar schedules it in May; the summer guide covers the why.

Before You Start

The warning signs

• Clothes take longer than one cycle to dry, or come out hotter than they used to.
• The top of the dryer is hot to the touch after a cycle.
• A burning or musty smell in the laundry room.
• Little or no airflow at the outside cap while the dryer runs, or a flap that does not open.
• Lint visible around the outside cap or behind the dryer.

Tools and materials

• A dryer vent brush kit with flexible rods that connect to a drill (the pick below).
• A vacuum with a hose and crevice tool, or a shop vacuum.
• A nut driver or screwdriver for the duct clamps, and a flashlight.
• Foil HVAC tape (not cloth duct tape, which dries out and lets go) and new clamps.
• Optional: a replacement semi-rigid or rigid metal transition duct if yours is foil, plastic, or crushed.

Step-by-Step

1. Pull the dryer out. Unplug it or shut off the gas as above, then walk it away from the wall far enough to work behind it. Have a helper for a heavy dryer.
2. Disconnect the transition duct from the back of the dryer and from the wall or floor duct, loosening the clamps. Note what you find: a crushed duct, a foil "slinky" duct, or a long sagging run is part of the problem and gets replaced in step 8.
3. Clean the dryer end. Vacuum the exhaust port on the back of the dryer and the lint trap housing inside the dryer (pull the trap and run the crevice tool down the slot). Lint in the housing is what starts fires closest to the heat.
4. Brush the duct from inside. Assemble the rods, chuck them in a drill on a low speed if the kit allows, push the brush into the wall duct, and work it in with the drill turning while the vacuum runs at the opening. Add rods as you go. Go slowly around elbows; forcing the brush can push a rod joint apart inside the duct. Pull the brush back and clear it, then repeat until it comes back clean.
5. Go outside to the cap. Remove the cap's cover or flap, pull out the lint packed behind it, and check for a bird's nest. Run the brush in from this end too, toward the house.
6. Fix the cap. If the cap has a screen over it, remove the screen: screens catch lint, clog, and are prohibited on dryer vents by most codes. The flap should swing freely and close on its own. Replace a cracked, painted-shut, or missing cap.
7. Vacuum everything you dislodged at both ends, and the floor and wall behind the dryer.
8. Replace the transition duct if it is not metal. The short duct between the dryer and the wall should be semi-rigid or rigid metal, as short and straight as possible, with no more than a couple of gentle bends. Foil, vinyl, and plastic ducts trap lint in their ridges, crush easily, and burn; they belong in the trash.
9. Reconnect. Clamp the transition duct at both ends and seal the joints with foil tape (never screws into the duct; the points catch lint). Do not use cloth duct tape.
10. Push the dryer back without crushing the duct behind it. Leave a few inches of clearance. Plug it in or turn the gas valve back on and check the connector for leaks with soapy water if you moved a gas dryer.
11. Test. Run the dryer empty on air-fluff and go outside: you should feel a strong, steady stream at the cap and see the flap fully open. Then run a normal load and confirm it dries in one cycle.

Troubleshooting and When to Call a Pro

The brush stops partway. A crushed section, a long run with many elbows, or a blockage the brush cannot pass. Do not force it. The run is very long, goes up through the roof, or terminates somewhere you cannot reach. Roof terminations and runs over about 25 feet are vent-service jobs with longer rods and a rotary tool. Airflow is still weak after cleaning. The duct may be crushed inside a wall, the run may be too long for the dryer, or a booster fan may be needed; a vent service can inspect with a camera. The dryer still overheats. Stop using it and have the dryer's thermostat and blower checked.

How Often

At least once a year for a typical household; every six months with pets, large families, or a long or twisting duct run. Clean the lint trap before every load, and never run the dryer while you are asleep or out of the house. If the outside cap is where you can see it, glance at it every month for a stuck flap or lint on the ground.

Frequently Asked Questions

Can I clean the vent with a leaf blower instead of a brush?

People do, from the dryer end toward the outside cap, but it blows lint into every ridge and elbow rather than pulling it out, can push a foil duct apart, and does nothing for a packed cap. The brush kit costs little more than a good lunch and actually removes the lint.

Is a foil flexible duct really that bad?

Yes. Its ridges trap lint, it crushes behind the dryer, it sags into low spots that collect lint and condensation, and the foil-on-plastic types burn. Semi-rigid metal transition duct is inexpensive and the swap takes fifteen minutes while the dryer is already pulled out.

How do I know if the duct inside the wall is metal?

Look at the wall stub-out behind the dryer and at the outside cap: a rigid metal duct shows as smooth galvanized or aluminum pipe at both ends. If either end shows plastic or foil, or the run is unknown, a vent service can inspect it with a camera and replace it if needed.

My dryer vents into the garage or attic. Is that okay?

No. Dryers must vent to the outdoors; venting into a garage, attic, or crawl space dumps moisture and lint into the structure and, for a gas dryer, exhaust. Have a proper vent run installed to the exterior.

The Bottom Line

Unplug or shut off the gas, pull the dryer out, clean the dryer end, brush the duct from both ends with the vacuum running, clear the cap and pull off any screen, replace a foil or plastic transition duct with metal, reconnect with clamps and foil tape, and test for strong airflow at the cap. An hour a year, and the dryer runs faster, cheaper, and safer. Add it to your calendar so it happens.

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