Dryer Exhaust Venting and Maintenance

Inspecting the Dryer Exhaust System

According to the Consumer Product Safety Commission dirty and clogged dryer vents are responsible for over 15,000 fires each year.

Professional home inspectors licensed by the Texas Real Estate Commission (TREC) can inspect multiple residential dryer exhausts every day. According to the Consumer Product Safety Commission dirty and clogged dryer vents are responsible for over 15,000 fires each year in the United States. TREC has a standard’s of practice that inspector’s follow to help better protect the consumer from these dangers:

Texas home inspector’s report the following as Deficient:  

(1) missing or damaged components;  

(2) the absence of a dryer exhaust system when provisions are present for a dryer;  

(3) ducts that do not terminate to the outside of the building;  

(4) screened terminations; and  

(5) ducts that are not made of metal with a smooth interior finish.

General Dryer Venting Guidelines

  • 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.
  • Flexible transition hose between the dryer and the wall outlet should be either the foil type or the aluminum flexible duct (most preferred). Do not use the plastic or vinyl.
  • Concealed ducting must be rigid metal (galvanized or aluminum) duct.
  • Duct joints shall be installed so that the male end of the duct points in the direction of the airflow.
  • Joints should be secured with metal tape (not duct tape). Do not use rivets or screws in the joints or anywhere else in the duct as these will encourage lint collection.
  • Length of concealed rigid metal ducting shall not exceed 35 feet (25′ for IRC). Deduct 5 feet from the allowable length for every 90 degree elbow and two and a half feet for every 45 degree fitting (the Dryer-Ell is an exception under 2006 IRC Section M1502.6, 2009 IMC Section 504.6.4 and 2009 IRC Section M1502.4). These lengths may vary per local codes and dryer manufacturers recommendations.
  • Dryer venting shall be independent of any other systems (chimneys or exhaust vents).
  • Termination of dryer venting must be to the exterior with a proper hood or roof cap equipped with a backdraft damper. Small orifice metal screening should not be part of the hood or roof cap as this will catch lint and block the opening in a very short time. The hood opening should point down and exhibit 12 inches of clearance between the bottom of the hood and the ground or other obstruction.

Dryer Exhaust System Maintenance Best Practices

  • Actually inspect the termination port of the dryer and the wall or roof cap. Look for birds nest or clogged openings. Most importantly, feel for proper exit velocity of the air leaving the vent and look at or feel the interior walls of the duct.
  • If you suspect clogged or partially clogged exhaust ducting, it is likely you need to have them cleaned. Dryer vent cleaning improves the safety and efficiency and depending on the venting circumstances, should be cleaned or inspected every 6-12 months.
  • Make sure your flex transition hose is not kinked or crushed. The space behind your dryer should be sufficient as to provide adequate room for the flex transition hose to make its bends with minimal deflection and restrictions.
  • Dryer vent cleaning is a very real commercial trade and the contracted work is sometimes described as Routine and Problem Cleaning.
  • Routine cleaning is done from the outside by sending an air-propelled “jet-snake” through the vent. It blows air 360 degrees backwards, blasting the lint loose and blowing it outside. The lint is caught in a special bag.
  • Problem Cleaning is performed when an individual dryer is not drying clothes fast enough. They disconnect and pull the dryer out, install a large blower on the vent, and blow, brush, vacuum and/or dismantle – whatever it takes to get the vent clean.
  • Look in your Yellow Pages under Duct Cleaning or search the Internet.
  • 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. I have created a very useful comparison page. Click here to view it.
  • Keep exhaust duct as straight and short as possible. Exhaust systems longer than the manufacturer’s recommendations can extend drying times, affect appliance operation and may encourage lint build-up on pipe lining.
  • When running the clothes dryer, be careful not to overdry. Running your dryer too long not only wastes energy but can also damage your clothes. We recommend using an automatic setting, such as “less dry” rather than a timed setting.
  • Clean lint filters regularly. Cleaning the lint filters on your washer and dryer will save energy, improve performance, and minimize fire hazards.

Signs of Lint Buildup

Is your laundry taking longer to dry? Do you have to run the same load twice? Is the top of your dryer hot to the touch after each use? Rather than a faulty dryer, clogged ductwork may be the culprit. The removable dryer lint filter catches most of the lint as it passes through a load of laundry. But, pieces of lint can sneak past the filter and get stuck in crevices along the dryer duct. When there’s a buildup of lint, airflow is restricted, which can lead to overheating. If the air inside the duct gets hot enough, it can ignite the lint and cause a dryer fire.

How To Clean A Dryer Vent

The tools and supplies you need to clean a dryer vent duct include a vacuum with a long hose attachment, dryer vent brush kit, screwdrivers and UL-listed metal foil duct tape. DIY cleaning job saves money, but we always recommend that a qualified professional perform any skilled work on your home.

Step one: The first thing you have to do is locate where the duct begins and ends. Most dryers will have a short 4-inch diameter exhaust in back that connects to the ductwork through an aluminum elbow. Hot air goes through those pipes and exits your house through an opening on an outside wall.

Step two: Safely disconnect your dryer by unplugging the power cord from the outlet or turning off the gas or propane valve. Remove any clamps or metal tape so that you can pull the dryer vent pipe free from the exhaust. If you own a dryer that runs on natural gas, be extremely careful you don’t disturb the dryer’s gas line when disconnecting the power. A gas leak is serious; call a professional if you’re unsure of the process.

Step three: Pull the vent pipe away from the wall duct. And then remove the duct cover from the exit point outside so that you have clear access to the entire ductwork. The dryer vent brush kit will come with a lint brush and flexible segments that you can connect together, depending on the length of your dryer ducts. You do need special vent brushes in order to effectively clean a dryer vent duct.

Step four: Insert the vent brush into the ductwork and spin it counter-clockwise while pushing the brush as far as you can down the dryer ducts. If you need more length to reach the other end of the duct, add another segment from your brush kit. The brush should loosen lint that has become lodged along the ductwork.

Pro tip: enter from the outside of the house if it’s located higher than the dryer. Gravity can help clear lodged debris and it’s easier to clean lint on your laundry room floor than have it clutter any landscaped areas. While you have the vacuum out, remember to clean out the inside of the dryer outlet as well.

Step five: Clean all of the lint that comes out of the duct work with a vacuum. (Heads up: It may be a lot!) Use the flexible hose attachment to clear out the openings on both ends, as well as the lint trap housing. Repeat as needed until there is no more existing lint that needs to be removed.

Step six: Put all of the dryer components back together and plug it in. Then give it a trial run before sliding it back into place. Check to make sure all of the venting remains connected and there are no gas leaks. Ensure that the outside dryer vent is well fastened and caulked to the building for added performance and to prevent moisture intrusion.

Safety Precautions to Consider

When you hook your dryer back up, avoid using a soft foil-style vent that connects to the wall duct, as these are a known fire hazard. These and other flexible plastic tubes are forbidden by most building codes. Go with an adjustable, rigid, 90-degree elbow at the exhaust end of the dryer instead.

Houston Area Home Maintenance Inspections

Imperial Pro’s affordable home maintenance inspections are our most utilized service that homeowners need the most. Whether you’re planning on selling your home in the future or staying in your forever home, you need to understand the condition of your home with an annual home maintenance inspection from Imperial Pro Inspection. Partner with Imperial Pro to protect and maintain your biggest investment to catch unknown issues before they become too expensive to manage. Spend a little now to save A LOT down the road.  Schedule your home maintenance inspection today. #lovewhereyoulive

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