DIY Fireplace Flue Replacement

Determine whether your chimney flue is stuck open or shut. Lay on your side so that you can look up into your chimney. Use a flashlight to locate the flue. Look for empty space between the chimney lining and the flue to verify that the flue is open. Place your hand into the chimney shaft to verify that you feel a draft coming through the chimney.

Mark a spot on the inside of your chimney shaft wall above the open flue with a piece of chalk. Select a spot that has 6 inches of straight, parallel wall space on either side of the chimney shaft.

Measure the length and depth of the marked spot with a folding carpenter's ruler. Write down these measurements in inches.

Purchase an inflatable chimney liner that is the size of your measurements or up to 6 inches larger in length and depth than your measurements. Buying the right size of inflatable chimney liner is important to ensure a tight and proper fit in your chimney and to effectively block air from entering into your home through the open shaft.

Lay your inflatable chimney liner flat on a table. Attach the inflation tube that came with the liner to the air valve on the liner. Turn the valve to the “on” position so that air can flow through the tube and into the liner.

Breathe into the tube to inflate the chimney liner. Blow about 10 breaths into the liner until it is loosely inflated but still maneuverable so that you can position it in the chimney at the marked spot.

Position the partially inflated liner into the chimney at the marked spot. Blow into the tube to inflate the liner completely or until it fills the chimney shaft, blocking air flow into the firebox. Test that you’ve inflated it properly by touching the liner with your finger; it should feel springy like your leg but not tight like a snare drum.

Turn the valve to the “off” position to lock the air in the liner. Let the tube hang down and tie a red notecard to it to remind yourself that the liner is in your chimney. Turn the valve to the “on” position, deflate the liner and remove it from the chimney before using your fireplace. Repeat the process after you’re done using the fireplace and when it is cold to replace the inflatable liner in the chimney shaft.