How to Check Your Ductwork for Leaks: 5 Simple Methods to Try

Leaks in ductwork are an expensive problem in three ways. First, ductwork that allows treated air, which means it has been heated or air conditioned, to escape is a waste of energy that causes higher utility bills. Next, ducts leaking, especially in unconditioned areas like the attic, basement or garage, cause your HVAC equipment to work harder, and that can lead to mechanical failure.

Finally, leaking ducts must be repaired, and that costs money. However, the cost of ductwork repair for leaking ducts will be recouped quickly when your energy bills are under control again.

Follow the steps and ideas below to help you learn how to check your ductwork for various leaks and improve the efficiency of your HVAC system.

How do I Know if My Ductwork is Leaking

There are a few telltale signs that will signify that your ductwork may be leaking. When leaks in your ductwork occur you will need to either examine the ductwork yourself or hire the job out to a professional HVAC technician. The following are a few clues that will provide signs that you may have some leaks within your ductwork:

  • Uneven heat/cool in your home
  • Various rooms are dustier than others
  • Higher-than-normal heating and cooling costs
  • You might hear the air escaping like a whistling or whooshing noise

How to Check Your Ductwork for Leaks – Ductwork Leak Testing

There are many methods for checking your ductwork for leaks. You can choose which method might work best for you and your situation.

  1. Look for obvious leaks, tears or separations in the ductwork. Inspect your ductwork system using a flashlight and simply look for any areas that are obviously leaking air. When you locate a leak, you should mark it somehow (take a picture or use a sharpie) or immediately seal the leak with foil backed duct tape or mastic.
  2. Turn on your HVAC system to full power or strength. If your heating and cooling system is blowing air strongly, it will be easier to locate any possible leaks.
  3. Check all the joints or elbows. Any place where ductwork is connected to other pieces of ductwork are prone to leaks. Also, any turn within the ductwork system is also susceptible to leaking.
  4. Look for older duct tape on the ducts. Duct tape that is on your duct system may be evidence that your ductwork was leaking in the past and someone might have tried to patch the leak. Duct tape is not a permanent fix. If you happen to see any duct tape on your ducts, remove it and then replace it with foil backed duct tape or use mastic to seal the leak.
  5. Use a smoke pencil. A smoke pencil is a tool you can buy at any home improvement store and they start at around $30. Move the smoke pencil slowly over the ductwork. When you see a disturbance in the smoke, you can suspect a leak to be present in the area.

How to Fix Leaky Ductwork

Once you locate and determine where the various leaks are within your ductwork system, it is very important you seal or fix the leaky ductwork. One way to do this is by simply hiring the job out to a professional HVAC technician. This will probably cost you around $200-$500 for the technician to fully fix all the leaks within your ductwork system.

A more cost-effective way to fix your leaks in your ductwork would be to do the work yourself. There are two main ways to fix the leaks in your ductwork, and both can be done relatively easily by the homeowner. The first method is to wrap the ductwork where the leaks are located with heat-rated foil-backed duct tape. A roll of foil-backed duct tape starts at around $12, and you may need multiple rolls depending on the number of leaks you have to fix. A longer-lasting method to fix leaks in your ductwork is by using a paint brush and mastic. Mastic will harden in a short period of time and completely seal the leaks in your ductwork. A half-gallon of heat rated mastic for ductwork will start at around $20. See the complete Pick HVAC How to Seal Ductwork Guide for details.

Frequently Asked Questions

How often should I inspect my ductwork?

You should inspect your heating and cooling system’s ductwork at least once a year. Start at the main unit and then follow all ducts all the way to the vents or returns.

How much does it cost to fix leaky ductwork?

If you locate leaks within your ductwork system you can fix this issue by yourself by going to a home improvement store and purchasing foil backed duct tape or mastic. The materials will cost around $30-$50. If you decide to hire a professional HVAC technician to seal up the leaks in your ductwork you can expect to pay around $100 for the initial cost and then around $35-$50 an hour, depending on where you live.

Can I fix leaky ductwork myself?

Yes!! You can absolutely fix leaks in your ductwork. Use either foil backed duct tape or mastic with a paint brush or caulk gun. If the leaks are too hard to access or you are not comfortable with trying to repair leaks you can hire a professional HVAC technician.

Why should I check for leaks within my ductwork?

Your attic and basement are often considered unconditioned spaces. These locations are where most of your ductwork will be located. You need to check these spaces for leaks in order for your heating and cooling system to work properly and efficiently.

Do it Yourself or Hire a Professional?

By using the steps, ideas, and instructions that are listed and discussed above you can absolutely check your ductwork for leaks by yourself and do not need to hire a professional. This is a job that just takes time and patience. Make sure that you inspect all the ducts and mark down any areas that are leaking and either seal up the leaks yourself or hire a professional HVAC technician to do the job of sealing your leaky ductwork.

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Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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