How to Check Ductwork for Leaks In a Few Simple Steps

August 18, 2023

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how to check ductwork for leaks

Is your HVAC system working overtime to keep your home comfortable? Do you suspect your ductwork may have some leaks? Checking your ducts for leaks and sealing any you find can help your system run more efficiently. 

How to check ductwork for leaks? The short answer is to carefully inspect all exposed and concealed ducts for gaps, detachments, and airflow, then seal any leaks found with aluminum foil tape.

Follow these simple steps to hunt down and seal duct leaks.

How to Check Ductwork for Leaks? First, Gather Your Supplies

Before you start sleuthing for leaks, gather the supplies you’ll need to seal them up. Here’s a list of ductwork detective must-haves:

  • Aluminum foil tape - The shiny silver stuff that sticks like glue. A true HVAC BFF.
  • Metal snips - Handy for trimming tape and cutting sheet metal if repairs are needed.
  • Rags - For wiping dust off ducts so the tape sticks better. Unless you like the ‘dusty duct chic’ look.
  • Flashlight - For peering into dark duct corners in search of leaks. Don’t forget the batteries!
  • Thick gloves - Protect your hands from sharp metal edges and itchy insulation.

Once you’ve got your gear, it’s time to start searching for the ductwork equivalent of Carmen Sandiego (if she was an air leak instead of a thief, that is).

cleaning bottles yellow rubber gloves and bucket

Inspect All Exposed Ductwork

The easiest place to start looking for leaks is in exposed ductwork like registers, vents, and main trunk lines. Shine your flashlight and closely examine each section. Listen and feel for air movement, and check for gaps, detached or loose tape, and damaged sections. Leaks often occur at joints and seams.

Tip: Run your HVAC fan while inspecting to help identify leaks. Just be sure to turn it off before sealing anything up!

Use aluminum foil tape to seal small gaps and holes. Cut a piece of sheet metal for larger damaged sections to cover the hole, then tape it in place. Make sure all seams and connections are tightly taped.

how to check ductwork for leaks


Check Hidden Ducts

Once you’ve sealed all the obvious leaks, it’s time to play detective with the hidden ducts inside ceilings, floors, and walls. Turn on your HVAC fan and make your way through the house, feeling along walls and listening at vents for obvious air leaks.

Use your hands to detect airflow from cracks and gaps leading into concealed ducts. Or get fancy with a smoke pencil - available at HVAC supply stores - to precisely locate hidden duct leaks. The smoke will get sucked into any openings. Just try not to set off the fire alarm with your smoke signals!

Accessing concealed ducts for repairs takes more work, but it’s worth it to plug the leaks. You may need to cut holes in walls or ceilings to apply tape. If that sounds intimidating, hire an HVAC pro to tackle it.

residential air ducts in attic

Do a Duct Blaster Test

For a thorough search, consider hiring an HVAC technician to perform a duct blaster test. This test pressurizes your ductwork to detect even minuscule leaks allowing air escape.

With a few small holes cut into the ductwork, a large fan is mounted to pressurize the system. Sensors determine the air loss rate to pinpoint leaks. It provides quantitative proof of duct leaks so you know exactly how much sealing is needed.

Though not always necessary, it’s the ultimate leak-seeking ductwork test for the most air-tight system possible.

technician performing a duct blaster test

Close Off Air Vents in Unused Rooms

Here’s one more quick way to eliminate duct leaks - seal vents and registers in unused rooms. This prevents conditioned air from escaping into those areas. Just be sure to remove the seals if you start using the rooms again!

AC vents

Now Get Sealing!

You can find and seal duct leaks with a simple checklist and the right tools. Take a methodical approach - inspect exposed ducts, check for airflow at hidden vents, and consider a duct blaster test. With a well-sealed duct system, your HVAC won’t have to work as hard to keep your home comfortable.

About 24/7 AC Repair Garland

Are you looking for an experienced, reasonably priced HVAC technician available around the clock? 24/7 AC Repair Galand is your #1 resource! Please call (214) 206-4356 to schedule an on-demand appointment.


How do I find an air leak in my ductwork?

To find air leaks in ductwork, inspect all visible ducts, vents, and registers for gaps, detachments, or loose tape, listening and feeling for airflow. For concealed ducts, turn on the HVAC fan and feel along walls or use a smoke pencil to detect airflow from cracks and openings leading to hidden vents.

How do you check for holes in ductwork?

To check for holes in ductwork, inspect all exposed and concealed ducts visually and use tools like smoke pencils or a duct blaster test to precisely locate any leaks allowing conditioned air to escape the system.

How many years do ducts last?

The expected lifespan of ductwork is approximately 20-30 years, after which ducts may need replacing due to buildup reducing airflow and efficiency over time.

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