How to clean the dryer vent and replace foil duct
Clean a dryer vent at least once a year, or sooner if clothes take longer to dry. Disconnect the duct, brush the full run to the outside and check that the outdoor flap opens. Replace plastic or thin coiled foil duct with smooth metal duct. Take extra care with gas dryers.
How often to clean a dryer vent
U.S. Fire Administration data for 2008 to 2010 put clothes dryer fires at about 2,900 a year in residential buildings, with about 5 deaths, 100 injuries and $35 million in losses. Failure to clean was the top factor, at 34%. Fires peaked in January, at 11% of the year's total.
| Job | How often |
|---|---|
| Clean the lint screen | Before or after each load |
| Vacuum lint around the drum opening | As it collects |
| Clean the vent pipe | Once a year, or sooner if drying takes longer (NFPA) |
| Check the outdoor flap | When you clean the vent, and after snow |
| Have a gas dryer's line and connection inspected | Periodically. NFPA gives no set interval |
New owner? Count the first cleaning as overdue. A full load of wet clothes can hold up to about a gallon and a half of water, and all that moist air carries lint into a duct you've never seen.
Tools and duct you need to clean a dryer vent
- A dryer vent brush kit with flexible rods that fit your drill or hand-turn
- A vacuum with a hose attachment
- A screwdriver or nut driver for the duct clamps
- Foil tape rated for ducts. Duct cloth tape dries out
- Replacement duct if yours is plastic, thin coiled foil, dented or crushed
- Work gloves, since metal duct edges are sharp
When you buy new duct, these are the figures in the model residential code, as printed in Seattle's 2018 edition. Your dryer's manual comes first, and your state may differ.
| Part | Model code figure |
|---|---|
| Vent duct | Smooth metal, 4 inches in diameter |
| Maximum length | 35 feet, unless the dryer's manual says otherwise |
| Each sharp 90° elbow | Takes 5 feet off the maximum |
| Each sharp 45° elbow | Takes 2½ feet off the maximum |
| Flexible connector | One piece, up to 8 feet, listed to UL 2158A, never hidden in a wall |
| Screws at joints | May not stick in more than ⅛ inch |
| Outdoor end | Backdraft damper, no screen, at least 3 feet from openings into the house unless the manual says otherwise |
How to clean a dryer vent, step by step
- Disconnect the dryer
Unplug an electric dryer. For gas, close the shutoff valve first. Slide the unit out slowly.
- Detach the duct
Loosen the clamps at the dryer and the wall. Check the duct for kinks, crushing or holes.
- Vacuum both ends
Clear lint from the back of the dryer, the wall opening and the floor behind the machine.
- Brush toward the outside
Feed the rods in slowly, turning clockwise so the sections stay tight. Pull lint out from the outdoor end.
- Clear the hood
Take off any screen, clean the flap and make sure it swings freely.
- Reconnect with sealed joints
Fit each duct section so the male end points in the direction of airflow, clamp it and tape the joint.
- Test it
Push the dryer back without crushing the duct. Run it on air and watch the outdoor flap open.
Warning signs of a clogged dryer vent
- Clothes need a second cycle or come out hot and damp.
- The top of the dryer or the laundry room gets unusually hot or humid.
- The outdoor flap barely moves with the dryer on.
- A burning smell. Stop the dryer, unplug it if it's safe to do so, and leave the area. Call 911 if you see smoke.
- A screen, mesh or cage over the outdoor vent. It traps lint, and the model code doesn't allow it.
- Nests or droppings at the hood. USFA notes that small birds and animals can block vents.
Clean a dryer vent yourself or hire dryer vent cleaning?
A short, straight run through an outside wall is a good DIY job. Hire a dryer vent cleaner for a long run, a roof exit, or a duct hidden in walls or ceilings with several bends.
With a gas dryer, shut off the gas valve before moving the unit, and move it gently so you don't strain the flexible gas line. If you smell gas, leave the house and call your gas utility from outside. Have a licensed plumber or gas tech handle any work on the line.
An electric dryer's plug and outlet should match, and the dryer must be properly grounded. Call a licensed electrician if the plug or outlet looks scorched.
What homeowners say about dryer vent cleaning
Pull the duct off and shop-vac it right away if you don't know when it was last cleaned. One owner blows out the run with a leaf blower. (Reddit)
Companies that sweep chimneys often clean dryer vents too, so one visit can cover both. One new owner had a whole bird's nest pulled out of the dryer vent. (Reddit)
Loads that suddenly take two or three cycles to dry are the warning sign. One owner found the duct packed solid with lint and the dryer's safety cutoff killing the heat. For long runs hidden in walls, owners hire a chimney or dryer-vent sweep because DIY brush kits can't handle the bends. (Hacker News, DIY Stack Exchange)
Dryer vent questions
How often should a dryer vent be cleaned?
NFPA says once a year, or more often if clothes take longer than normal to dry. Clean the lint filter before or after every load as well.
Is flexible foil dryer duct safe?
The model code calls for smooth metal in the vent run and allows only a single listed flexible connector behind the dryer. Replace plastic or thin coiled foil, and look for the UL 2158A label on any flexible connector.
How long can a dryer vent be?
The model residential code allows 35 feet, minus 5 feet for each sharp 90° elbow and 2½ feet for each sharp 45° elbow. Your dryer's manual can set a different limit, so check it and your local code.
What you’ll need
Sources: U.S. Fire Administration, NFPA, seattle.gov
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.