Use smooth rigid metal duct for everything inside walls, ceilings and the attic, and a short semi-rigid metal connector listed to UL 2158A, 8 feet or less, behind the dryer. White vinyl hose isn't allowed. Thin foil accordion hose crushes easily and traps lint, so replace it too.
The four types side by side
| Type | Behind the dryer | Inside walls and ceilings | Airflow | Our take |
|---|---|---|---|---|
| White vinyl (plastic) | No | No | Poor | Replace now |
| Foil accordion | Only if listed to UL 2158A | No | Poor | Replace |
| Semi-rigid aluminum | Yes, if listed, 8 ft max | No | Good | Best connector |
| Rigid metal, smooth | Yes | Yes | Best | Best for the main run |
The "behind the dryer" piece is called the transition duct or connector. It joins the dryer to the duct in the wall. The rules for it are different from the rules for the duct itself, which is where most of the confusion comes from.
Each type explained
White vinyl hose
The ribbed white plastic hose that came with many older dryers. It melts and burns, sags into low spots that hold lint and water, and isn't allowed by the building code. If you have it, replace it, even if it looks fine.
Foil accordion hose
Thin aluminum foil over a wire coil. It's cheap and stretches to fit anything, which is the problem. The deep ribs catch lint, it crushes flat when the dryer is pushed back, and it tears easily. A few foil connectors are listed to UL 2158A and are allowed behind the dryer. Most of the thin foil sold at hardware stores isn't. Foil is never allowed inside a wall or ceiling.
Semi-rigid aluminum
Thicker aluminum that bends by hand and holds its shape. It has shallower ribs than foil, resists crushing, and comes in listed versions. For the hose behind the dryer, this is what we install.
Rigid metal duct
Smooth round metal pipe, joined with elbows. It has the least drag and lets lint slide through instead of catching on ribs. The Florida Building Code requires smooth metal duct at least 28 gauge (0.0157 inch) for the main run. If your vent passes through a wall, ceiling, floor or attic, this is the only right answer.
The label to look for
For the connector behind the dryer, look for UL 2158A, the safety standard for clothes dryer transition duct, printed on the package or the duct. No listing means it hasn't been tested for this use, whatever the package photo shows. Your dryer's installation manual may also name the connector types it allows; follow it.
Size and length
- Diameter: 4 inches for household dryers. Don't step down to a smaller size, and don't go bigger than the dryer's outlet without the maker's approval.
- Connector length: one piece, 8 feet or less, and never hidden in a wall, floor or ceiling.
- Main duct length: up to 35 feet, minus 5 feet for each 90° elbow and 2.5 feet for each 45°, unless the dryer maker allows more. Details in our Florida dryer vent code guide.
- Shorter is better. Use the shortest connector that reaches. Extra hose sags and bunches up behind the dryer.
Installing it right
- Unplug the dryer. On a gas dryer, turn off the gas valve.
- Cut the connector to length if needed, keeping it as straight as possible.
- Slide each end over the dryer outlet and the wall pipe at least an inch, and tighten a metal clamp on each.
- Seal rigid duct joints with foil tape. Point the male end of each piece in the direction the air flows.
- Don't use screws in any joint. Their tips catch lint.
- Push the dryer back slowly and check that the connector curves gently without crushing.
- Run the dryer on high and check the airflow outside.
Prefer to have it done? We carry listed semi-rigid connectors on every truck. See transition hose replacement.
Tight spaces behind the dryer
In many Pinellas condos and townhomes, the dryer sits in a closet with only a few inches behind it. A long hose there always gets crushed. Better options:
- A slim periscope connector, a flat rectangular metal duct that fits in a few inches of space. Choose a listed one.
- A recessed dryer vent box set into the wall, so the connection sits back from the wall surface.
- Rigid elbows instead of a hose, if the dryer and wall pipe line up.
- Moving the vent when the existing route can't work. See dryer vent rerouting.
What do I have?
- White and plastic: vinyl. Replace it.
- Shiny, thin, crinkles when you squeeze it: foil. Check for a UL 2158A label, and plan to replace it.
- Thicker aluminum that holds a bend: semi-rigid. Fine if it's 8 feet or less and not crushed.
- Smooth round pipe: rigid metal. Check joints and support.
Can't see the duct inside the wall? An inspection with a camera shows what's in there.
Want it done for you?
Same-day dryer vent service across Pinellas County. Standard cleaning from $99, airflow tested before and after, price before any extra work.
Clearwater team
1727 Coachman Plaza Dr
(727) 454-0061
Clearwater area
Largo team
13801 Walsingham Rd
(727) 662-5045
Largo area
Seminole team
7821 Seminole Blvd
(727) 855-3490
Seminole area
Questions
Is foil dryer vent hose up to code?
Only behind the dryer, only if it is listed to UL 2158A, and only up to 8 feet. Foil is never allowed inside walls, floors or ceilings. Most thin foil hose sold in stores isn't listed.
Can I use a vinyl dryer vent hose?
No. White vinyl hose isn't allowed by the building code and can melt or burn. Replace it with a listed semi-rigid metal connector.
How long can a dryer vent hose be?
The connector behind the dryer can be up to 8 feet, in one piece. The main duct is limited to 35 feet, less 5 feet for each 90° elbow, unless the dryer maker allows more.
Should dryer vent joints be taped or screwed?
Clamp the connector ends and seal rigid duct joints with foil tape. Don't use screws, which stick into the duct and catch lint, or cloth duct tape, which dries out.
What size is a dryer vent hose?
Household dryers use 4-inch duct. Don't reduce it, and match the dryer's outlet.
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