How to Install a New Dryer Vent

Choose the path before you buy the vent

You may only need to connect a dryer to an existing wall hookup, or you may need a new path through an exterior wall. We'd map the full route before buying materials, because its length and turns have to fit your dryer's limits. A short, direct route also vents most efficiently.

A dryer takes air out of the room. Without enough replacement air, combustion exhaust can be pulled indoors instead of going up the flue. If the assessment finds backdrafting, have the professional address the room's fresh-air intake.

Give the exhaust a real outdoor endpoint

Plan a path that carries the exhaust directly outside. An attic, crawlspace or other building cavity isn't an outdoor endpoint. Exhaust moisture can damage the building, including leaving crawlspace insulation damp, moldy and rotting.

Venting inside can also encourage mold and reduce indoor air quality, potentially aggravating asthma and other breathing problems. Keep devices that filter lint and return exhaust heat to the house off your shopping list, because they return unwanted moisture too.

Measure the route and gather the parts

Use a measuring tape to follow the exact route from the dryer exhaust to the proposed exterior outlet. Follow the corners instead of measuring diagonally across the room, and write down the bends alongside the distance.

Favor a short, straight, horizontal path. Extra length, upward angles, narrow passages and bends increase resistance to airflow and can contribute to lint buildup. Bring your measured route, bend count and dryer installation requirements to an installer if the path looks unnecessarily indirect.

Keep the exhaust run to outdoors separate from the transition connector behind the dryer. We'd choose rigid aluminum or galvanized steel for a new run because it holds its shape better and tends to trap less lint than flexible ducting. Match every part to your dryer's installation requirements.

Leave plastic, vinyl, nylon, foil duct and PVC pipe off the materials list. Foil tape is for sealing joints; it is a different product from foil duct.

Count the bends before cutting duct

For the wall-to-outdoor run, a common calculation allows 35 feet including the equivalent length of fittings. Under that calculation, each 45-degree bend uses 2.5 feet and each 90-degree bend uses 5 feet of the allowance. Your dryer's model instructions and local code set the final limits for your installation.

These are examples, not permission to use either length on your dryer. Compare the measured route and elbow count with your model's installation instructions before making an opening.

The listed transition duct behind the dryer can be up to 8 feet under the outdoor-vent guidance. Maytag's general hose guidance gives a shorter 7¾-foot limit, including flexible metal used in the system. Select the shorter length your appliance instructions require, and leave very little slack so the connector won't sag or kink.

Connect a dryer to an existing hookup

Start with an outdoor hookup whose duct and hood are in good condition. These connection instructions (opens in a new tab) show the cleaning, measuring, trimming and attachment sequence. Use them alongside your dryer's installation instructions.

1. Unplug an electric dryer before moving it. Have a professional handle the gas line before a gas dryer is moved. Disconnect the old connector, remove accessible lint and vacuum the dryer outlet, wall opening and outdoor hood. You should have a clear connection at both ends. If the fixed duct is clogged or damaged, have it cleaned or repaired before attaching a new connector. Follow the preparation steps to clean the dryer vent and outdoor exhaust.
2. Measure the dryer-to-wall distance along the path the connector will take. Mark the metal connector with about half an inch of overlap and, wearing protective gloves, trim it with tin snips. It should reach both outlets without looping. If the fit would crush it, ask about a wall inset or telescoping rigid metal transition duct.
3. Slip a vent clamp over one end, fit that end over the wall outlet and tighten the clamp with a screwdriver. Gently tug to check the joint, then clamp the other end to the dryer exhaust. Foil tape can secure the joints instead. Both ends should stay attached; if either moves, refit and tighten it before continuing.
4. Guide the dryer into place while watching the connector. It should remain short, straight and supported, without a kink or crushed section. If it changes shape as you move the dryer, pull the dryer forward and adjust the connection.

Don't use ordinary duct tape or screws that stick into the duct. Ordinary tape isn't intended for dryer-exhaust heat, and lint can catch on protruding fasteners.

Build a new run through an exterior wall

A new opening adds wall work and weatherproofing to the connection job. Contact a dryer-vent installation professional if you need help choosing the opening or fitting the duct through the wall. Give them your route measurements and dryer requirements.

1. Choose the outdoor outlet location before cutting. Keep it at least 3 feet from doors, windows and other building openings, away from fresh-air intakes, and at least 10 feet from an AC or heat-pump condenser. Favor an exterior wall over a roof outlet. You should be able to point to a direct outdoor endpoint; if the route only reaches a building cavity or needs an indirect path, have an installer revise it.
2. Mark and cut the wall opening to fit the hood you've chosen. As one product example, a Lambro wall vent calls for a hole ½ inch larger than its pipe; use your own hood's installation dimensions. The pipe should fit the opening without forcing it. If the wall assembly or cut is outside your experience, have the installer make the opening.
3. Fit a hood with a closable backdraft damper, with its opening facing down and at least 12 inches above ground. A louvered damper is more effective than a single hinged door. Leave off any screen, which can trap lint. Flash the wall penetration so the flashing connects to the existing wall's water-control layer, then caulk around the exterior hood. A trim block with metal cap flashing and a drip edge is one example for a matching wall assembly. If you can't identify the wall's water-control layer and assembly, have a qualified installer handle the flashing. The finished hood should be weatherproofed and its damper free to move. Use the outdoor vent requirements (opens in a new tab) while checking its placement.
4. Assemble smooth-interior, 4-inch metal duct from the indoor termination to the outdoor hood. Point joints in the direction of airflow, support the duct at least every 12 feet and at every joint, and seal the joints with foil tape. It should have no sags. Where possible, slope a horizontal run down toward outdoors by ¼ inch per foot; insulate duct in unconditioned spaces, especially in cold climates.
5. At the indoor end, fit a short UL-2158A-listed transition duct between the wall duct and dryer, joining it with clamps or foil tape. Move the dryer into place without crushing or looping the connector. If the connector cannot stay straight in the available space, ask the installer about a wall inset or telescoping rigid metal transition duct before using the dryer.

Questions that come up before the first load

A new vent still needs ongoing lint care. Keep the dryer's lint filter in place and clean it before or after each load. Arrange professional exhaust-duct cleaning at least once a year, and have a professional clean and service a gas dryer regularly. For the route through the whole system, follow the steps to clean the dryer duct from the trap to the outside.

Check the finished vent while the dryer runs

Before the first load, check the connection you can see and the hood outside. We'd do this while the installation is still easy to correct, because a crushed connector or closed damper can restrict the new route.

1. Look over the connector and accessible duct joints. The connector should be straight and every joint sealed, with no visible gap, sag or kink. Refit a loose connection and seal the joint before running the dryer.
2. If a gas dryer was moved, have a professional reconnect the gas line and confirm there are no leaks before you run it. Run the dryer and check from outside that the hood flaps move freely. If they stay shut, turn the dryer off and inspect the route for a kink or blockage. Contact the installer if you cannot clear the problem.
3. If your dryer provides a vent blockage test, run it using the model's instructions. Samsung dryers are one example with this installation check. If the test reports a blockage, correct the duct problem and repeat the test before the first load.