The maximum developed length of a clothes dryer exhaust duct shall not exceed 35 feet from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet for each 45-degree (0.8 rad) bend, and 5 feet for each 90-degree (1.6 rad) bend.
The International Association of Certified Home Inspectors (InterNACHI) establishes length requirements for dryer vents. The length cannot be more than 25-feet; it should also be as straight as possible. If there is a 90-degree angle in the vent, then it shouldn't be more than 20-feet.
Too long of a vent puts extra strain on the dryer. It's also a safety hazard because the reduced airflow can allow lint to build up in the pipe.
M1502.
According to the M1502. 5 code, the construction of a dryer duct has to be a minimum of 0.4 mm thick with a smooth interior. This means ribbed vents are no longer being used. Additionally, all duct joints must point in the direction of airflow.
Some dryers can exhaust beyond 25 equivalent feet without a booster fan. Dryer Duct Booster Saves significant energy - reduces drying times 50% or more. Reduces lint build-up, dust & fire hazards by maintaining proper velocity in duct runs up to 150 equivalent feet.
The maximum length of the exhaust duct does not include the transition duct. This means that vents should also be as straight as possible and cannot be longer than 35 feet. Any 90-degree turns in the vent reduce this 35-foot number by 5 feet, since these turns restrict airflow.
DO NOT terminate dryer vents in crawl spaces or attics. Dryer vents that terminate in crawl spaces or attics allow for moisture to deposit and encourage mold growth and health hazards. Dryer vents must terminate outside of the building.
Per the requirements of the International Residential Code, Section M1502 (2009-2021 IRC), the clothes dryer exhaust duct should be a rigid or semi-rigid metal duct made of galvanized steel or galvanized aluminum with a smooth interior finish and a duct diameter of 4 inches.
Dryer venting tips and practices
All dryer ducting must be a minimum of 4" in diameter. Clean, unobstructed, frictionless ducts encourage air flow efficiency, quickens drying times, adds longevity to clothing's life and reduces utility bills.
It is not safe. Vent hoses are necessary for dryers to operate properly because they allow heat, lint, and humidity to be vented outdoors. When a dryer is used without one of these vent hoses, moisture and lint can build up inside the appliance and even cause a fire.
If you're purchasing a gas dryer, the dryer vent must be long enough to extend outside. When a vent is installed properly and has the proper length, the lint which leaves the lint filter will be blown outside. If there is a collection of lint within the ducting of the dryer, this is a warning that the air flow is poor.
While PVC is meant for plumbing and venting applications, PVC is not approved for venting a clothes dryer as it is not heat rated. PVC pipe should not be used for this application.
If you use your dryer for too long, or if you leave the door open while drying clothes, then you could end up with a fire. Electric dryers catch fire often because they are designed to heat up quickly, so they overheat easily. They also have a fan that sometimes can blow hot air into the room.
If yours is too long, you can use scissors to cut the hose and wire clippers to cut the circular wire that gives the hose its shape. Make sure to attach the clamps! Usually dryer vent hoses come with clamps.
Route the dryer vent horizontally to the home's outside wall. Duct work should pitch 1/4-inch per foot to the outside. This keeps moisture out of the pipe. For basement laundry areas where your ductwork will run vertically to the outside wall, you may need to use 90-degree elbows.
Here's a quick rundown: If you can't vent your dryer outside, there's a risk of fires due to lint buildup, a chance for mold to grow, your laundry room might get too hot, and drying times could increase, possibly causing damage to your clothes and higher energy bills.
The standard maximum distance your dryer duct can run is 25 feet from end to end. Some brands can go up to 35 feet, but you'll need to check manufacturer instructions and local regulations.
The maximum length of a 4-inch (102 mm) diameter exhaust vent shall not exceed 35 feet (7620 mm) from the dryer location to wall or roof termination, and shall terminate with a full opening exhaust hood. A reduction in maximum length of 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend shall apply.
Shortening your dryer vent hose is a simple project that can yield significant benefits. If you already have tin snips, the cost can be as little as $5 to $10 for a roll of foil tape and a pair of vent hose clamps.
Flexible duct collects lint.
The typical maximum-allowable duct run for dryers is 25 ft.; anything longer than that requires a booster fan. The 25-ft. limit presumes a 4-in. -dia.
In situations where outdoor venting is not an available option, the vent bucket serves as an efficient indoor solution. It collects lint and moisture, ensuring they do not disperse throughout your living area. It is particularly convenient for apartments or temporary setups.
Dry Vent Rules
Any dry vent must rise at least 6 in. vertically above the flood rim of the fixture before turning horizontally or connecting to a vertical vent pipe. The horizontal run must be sloped to allow any condensation that forms within the pipe to run back to the drain.
The flexible nature and expandable configuration allow most installs to occur without any modification to the duct or the wall penetration. A pair of jumbo zip ties and you're good to go…at least for a few months until all of the internal bumps and ridges begin to clog with lint.
Dryer cords are usually a maximum of six-feet-long as the code requires that an outlet be close to the connected appliance. Check to see if you need a 3-prong vs. 4-prong dryer cord and take that into consideration when shopping for new appliances.
A: The tape is flammable and burns very well so I would not recommend it.