Complete Guide on How To Connect Flex Duct Together

A flex duct is a long ductwork tube. It is more adaptable to difficult living environments than inflexible ducting. Many HVAC blend rigid and flex air ducts to establish a duct network. Because that is the best use of the available space in the house. A flexible duct is an excellent ventilation device for a wide range of applications. But hurried installations can produce poor-quality outcomes. MMI shows how to connect flex ducts. We’ll go through that in this article.

Flex ducts joining

You need flex ducting to cover a greater distance than the length. In this case, you’ll need to connect more than one length of flexible duct. It’s worth mentioning that flex ducts work to spiral. The flex is the female component, or large end, whereas the fittings are the male part. You’ll need a male connection piece to connect two lengths of flexible ducting. There are many sizes of flex duct connectors. But you must use the appropriate size to fit the size of your duct. It’s a good idea to use j-clips to keep the flex ends taut around the coupler.

Step-By-Step Instructions for Connecting Flexible Ductwork

  • First, get the necessary components.
  • You’ll need two lengths of flexible ducting, a male connection piece, and two j-clips to join two lengths of flex together.
  • Begin by removing the worm drive hose clamps. Then, slide them over the flexible ducting’s ends.
  • Next, take your male coupler and wrap the flexible ducting around both ends of the connector.
  • Tighten the j-clip by positioning it over the flex covering the metal coupler. Use a screwdriver or a battery drill equipped with a 7mm hex head drill bit to complete this.


Route the flexible duct with the fewest bends and the smallest degree of bend at each turn. Avoid bending ducts across sharp corners or any way that makes them contact metal fittings, pipes, or conduits. When making bends, keep the bend radius to one duct diameter. For each duct run, take the most direct path. And the shortest length of duct required to make the connection. Do not install ducts in a compressed state or at an excessive length. According to Mold Air Duct Cleaning Alpharetta, it will increase friction losses. Avoid routing in areas where the duct materials expose direct sunlight or near a UV source. UV light has the potential to damage several duct materials. Routing ducts near hot equipment hotter than the approved flex duct-use temperature can harm the duct.


Support horizontal duct runs with 1-1/2-inch least hanger/saddle material. Support intervals should be the manufacturer’s instructions or your local code. But only at a distance of 5 feet, stated by HVAC cleaning alpharetta.
Long duct lines with steep bends may need more support before and after the bends.

The most allowable sag is 1/2 inch per foot of support length. For supporting ducts in attic spaces, ceiling joists provide suspension straps. Protect the duct from damage caused by the metal collar’s edge. The duct should have more support between the metal connection and the bend. It permits the duct to run straight for a few inches before bending. Some local codes may prevent the use of vertical flex ducts.

Connecting and Joining

You may need to connect your flex ducts to an existing duct at times. First, calculate the distance between the ducts that your flex duct will span. Cut the flex duct to the desired length with a utility knife. Snip the wire helix with wire cutters. If you’re working with an insulated flex, the next step is to remove the outer jacket and fiberglass insulation from the inside foil layer. Next, run a bead of mastic sealant along the duct’s end. Slip the flex duct over the mastic glue and the other duct. Ensure the duct extends at least one or two inches beyond the outlet. Tighten the clamp with a screwdriver or a battery drill. 

Cleaning of the Flexible Air Ducts

According to HVAC Cleaning Alpharetta, cleaning is important. Flex ducts running through unconditioned areas should have air space on both sides. Moisture can collect on a flex duct that is not ventilated. This moisture can cause harm to the surroundings as well as lead to fungus development. Keep both flex air ducts dry during and after construction. You can also learn how to install flexible air ducts. When it becomes wet, the insulation can stay moist for years. As a result, it can create a breeding environment for fungus growth. Duct boots, particularly floor ducts, should also be clean throughout and after construction.

Standards by Professionals

Each UL 181-listed flexible duct manufacturer includes installation instructions with each packaged product. These include detailed instructions on how to create correct connections and splices. The UL 181B Standard includes these processes and the materials necessary. The purpose of these standards  is to provide a secure connection for air ducts.
Avoid these mistakes

Following are the mistakes that HVAC Cleaning Alpharetta recommends you avoid during the process.

  1. You can reduce friction by extending the duct to ensure it is taut and does not sag.
  2. You can use metal or plastic support straps, such as suspension clips or wire rope for support in both vertical and horizontal ducts.
  3. You must also guarantee that all bends have a bend radius greater than one duct diameter. Finally, remove any extra duct length by cutting it off.
  4. If you have any concerns or need professional help, contact Mold Air Duct Cleaning Alpharetta. They have everything it takes to help your company with any ducting!

Also Read: Why Custom Packaging Is Better Than Simple Boxes?

Total Views: 171 ,
By Cary Grant

Leave a Reply

Your email address will not be published.

Related Posts