How to plug a round 8″ flue pipe with a swivel damper?

How to plug a round 8″ flue pipe with a swivel damper?

Q: Hi Jason, Here are a few pictures of my fireplace damper and round flue pipe. The diameter is 8″ in the flue pipe. What size Chimney Balloon do you suggest? – LG

A: Hi LG, This application is one of the most common styles of damper and flue that we run into. These pre-fabricated fireplaces are very common, but the butterfly damper that you have there is notoriously leaky. The great news is yours looks like it has never been used, so you will have no soot to deal with when you install a 9×9 Chimney Balloon. Take the deflated Chimney balloon and slide it in past the open damper. Put a couple of puffs of air into it and make sure it is installing nice and horizontal. Then inflate it the rest of the way until it tightens up, and close the valve. The 9×9 install is very easy to do. – Jason