How To Fix A Flex Air Duct Leak

If you notice increased energy bills or your home air conditioner isn't cooling properly, there could be a flex air duct leak. Not only do leaky air ducts cost money, but leaks cause poor air quality from all the debris trapped in the system. It is possible to fix leaky air ducts yourself. Here are tips to fix the problem.

Prepare to Work

For this project, you need:

  • work gloves
  • safety glasses
  • drop light and extension cord (optional)
  • damp rag
  • scraper
  • pliers
  • putty knife
  • fab mesh
  • paint brush
  • panduit straps (zip ties for flex ducts)
  • staple gun (optional)
  • mastic caulk
  • air duct mastic sealant .

Turn the unit ON, but not AUTO. Feel the duct joints and connections between ducts for leaks. Mark the leaky spots and turn off the unit. Run a drop light on an extension cord to the area, if needed.

Seal Loose Flex Ducts

Clean dirt from the ducts with a damp rag. Scrape old sealant carefully with a metal scraper. If it is connected with duct tape, pull it off the joint.

If the flex duct is loose, remove the old panduit strap from the inside of the tube. Otherwise, check for panduit straps on the outside of the tube and the inside of the tube. Peel back the outside layer and the insulation up to eight to twelve inches to reveal the inner layer, and detach the straps.

Push the inside layer back on the boot connection and add a new layer of duct tape. Install a panduit strap with the pliers, spread mastic sealant on the tape, and let it dry. Use a space heater or fan to speed drying, if desired.

Connect a panduit strap to the outer layer, and brush on mastic sealant on seams and connections. Add caulk to fixed seams using the putty knife and let it dry.

Repair Ripped Flex Ducts

If the flex ducts are ripped, clean the tube with a rag. Press the ripped seam together, and secure it with duct tape. If the rip won't stay with duct tape, use a staple gun, then attach the tape.

Fill large spaces with insulation before you seal them. Set the fab mesh over the crack, spread mastic sealant over the tape, and let the sealer cure. Spread mastic caulk on all fixed seams with a putty knife then let it dry.

Restore power and watch for leaks. Fixing flex duct leaks is a simple repair. If the unit still doesn't work or you don't trust your skill, contact an HVAC service such as Getzschman Heating, LLC.