Took me 5 years to realize I was oversizing my flue liners

I was up on a job in Portland last month doing a reline on a big old masonry chimney. Customer had been getting smoke spillage every time they used their fireplace. I figured the old liner was just shot, so I ordered the same 8 inch size I always use. When I pulled the old one out, I noticed the flue tiles were actually 6 inches, someone before me had already oversized it. I crawled up on the roof to double check the measurements and it hit me. I had been running 8 inch liners on 6 inch flues for years without even thinking about it. The math on draft velocity finally clicked in my head. Now I'm wondering how many other sweeps out there are just grabbing the same size liner without checking the actual flue dimensions? Anybody else have a moment like that where you realized you were doing something the wrong way for years?

2 comments

2 Comments

ellis.jennifer29d ago

You put an 8-inch liner on a 6-inch flue for half a decade?

cameron_palmer29d ago

Jeez louise, that's a real gut check right there. I mean, you just get on autopilot after a while, grabbing the same liner you always grab, especially when you're up on a cold roof trying to beat the rain. It's crazy how easy it is to miss something that basic when you're focused on just getting the job done, but that draft math is no joke. Once you mess with the cross-sectional area like that, you're basically strangling the fire's air supply before it even gets started.