Q&A – Where Does the Flue Pipe Cap Go?

A Florida homeowner wanted to confirm the placement of his newly installed furnace flue pipe cap.  

A homeowner in Florida, Robert J., had this question about a newly installed furnace flue pipe cap: 

Recently I had a new furnace flue pipe cap put on. It goes inside the pipe and not over it. The person I hired said, “Yes, it is seated down in the inside pipe that has clips that keep it in place.” The storm collar rests around the outside of the pipe...My question is should the cap be over the outside of the pipe or is it sometimes done on the inside? He put screws and caulking to keep the cap in place. I don't know any better, but would think it would go over outside of pipe. Thanks for your assistance.

Our resident expert roofer, John Stout with Go Roof Tune Up™, had this to say in response:   

The Flue Pipe Cap is sized to go inside the flue pipe. It is usually installed on the inside. With screws and caulking to keep the cap in place, you have a very good installation. The storm collar is on the outside of the pipe. It serves as a secondary seal at the point of the roof flashing.  

It appears from your detailed description, that the flue pipe cap is installed properly and you should have no concerns. When you have your qualified roofer do your regular roof maintenance, mention your concern regarding the flue vent cap. 

Thank you very much for your question! 

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Comprised of certified roofing professionals and expert craftsmen with a senior management team of a combined 140 years of roofing experience, Go Roof Tune Up™ is the premier provider of roofing services including repair, maintenance and replacement. Go Roof Tune Up™ inspects your entire roof system, and provides a written report with photos on every property we evaluate. We currently offer services in a number of States and the list is growing regularly. We work with homeowners, real estate professionals, property managers and home investors.