The use of the white vinyl flex pipe is all but completely prohibited, both by building departments and appliance manufacturers. Some municipalities allow or do not discourage the foil covered vinyl flex but almost all appliance manufacturers insist on the use of the aluminum flexible pipe.
Flex lines on a dryer are not a good idea, especially on a gas one - they can and do restrict the air flow, collect lint, and pose a fire hazard. Use solid ductwork instead, and you'll shorten the drying time since the air will flow better, and help prevent lint buildup.
In summary, while flexible accordion piping may seem like a convenient option for dryer venting, a hard pipe provides better airflow, fire safety, durability, and aesthetics. Investing in a hard pipe may cost a bit more upfront, but the long-term benefits make it a worthwhile investment for any homeowner.
Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths not to exceed 8 feet, and shall be listed and labeled in accordance with UL 2158A.
A friendly #PSA, every dryer manufacturer has a warning ⚠️ label that says do NOT use plastic of foil duct. They can be a potential fire hazard AND the necessarily contribute to poorer airflow. After being hung up on twice by a local appliance store for attempting to have a friendly civil conversation to simply share.
Rigid Metal Ducting: Rigid metal ducting, such as aluminum or galvanized steel, is widely considered the gold standard for dryer vent systems. These materials are non-combustible and can withstand high temperatures, reducing the risk of fires.
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.
Spiral-duct designs often trap lint and should not be used. The use of PVC pipe for dryer exhaust ducts is also not allowed by modern building standards.
Disadvantages of Flex Duct
Flexible ducts are more prone to air leakage around the seams, which can lead to lower HVAC system performance. Additionally, the pliable nature of flex duct tends to make them prone to tangling or crushing when they pass through tight spaces or fixtures.
Although dirty, this break allows heat and moisture to escape and limits your immediate risk of a dryer fire. PVC piping will not do this which leads to water pooling and severe clogs. These clogs will cause your dryer to overheat and become a potential hazard.
The general rule of thumb is that your dryer vent shouldn't exceed 25 feet (7.6 meters) in total length. If you have gas dryers, then, these dryers can have vents up to about 35 feet long because they have stronger fans. However, there's a catch! Every bend and turn in the vent acts like a speed bump for the airflow.
A rigid metal duct tends to be the best type of dryer vent hose. This tube provides a straight, direct line to the outside. Its inner wall is smooth, and it lacks the ribs found in flexible dryer hoses.
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.
Some dryer vent installations also have an external lint trap, which is also known as a secondary dryer lint trap or a 4″ In-Line Dryer Lint Trap.
No! Do not use duct tape to seal a hole in your dryer vent or connect it to the wall or for any other reason. Duct tape should also not be used on your air ducts. Duct tape is a common household item but poses a serious threat to the safety and health of your home when used on dryer vents.
Dryer vent hose damage: Tears, holes, or cracks will weaken the hose, making it more prone to falling off. Wear on the hose clamp: Dryer hose clamp damage could prevent it from holding the hose tightly enough.
Vent Type and Length
Any Dryer ducting used must be UL-listed. UL now requires that all Dryers be installed with either rigid or flexible metal ducting. Rigid is preferred. A UL-listed semi-rigid Dryer duct can be used if the vent length is 8 feet or less.
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.
A summary of the typical codes relating the dryer venting is as follows: Dryer vent systems shall be independent of all other systems and shall convey the moisture to the outdoors. Terminations shall be a minimum of three feet from property line and 12" above the ground and not exhibit any type of screen.
504 requires a dryer exhaust to be vented to the outside. This has been in the code for many years. There is an exception for a ventless dryer but the dryer has to be listed and labeled. Also the room where the listed and labeled dryer is installed shall have a 70 cfm exhaust fan and a floor drain.