Drove past an old job site in Portland and it changed my mind about liner thickness

I used to always go with the thin 316L flex liners on everything. Thought they were easier to install and good enough. But last week I was driving by a house in the Pearl District I worked on about 5 years ago. The owner was out front getting a new liner put in. I stopped and talked to the crew. Turns out the thin liner had developed a couple small pin holes near the top bend. Probably from acidic creosote over time. The new guys were putting in a heavy wall 304 liner instead. I helped them pull the old one out and you could see right where it failed. Now I'm totally rethinking my whole approach. Has anyone else seen thin liners fail after only a few years like that?

2 comments

2 Comments

maxhart7d ago

Yeah I had a 316L flex liner pinhole in under 4 years on a high-efficiency gas furnace. Switched to 304 heavy wall after that and haven't had a call back since.

abby_martin286d ago

Were you running that 316L on natural gas or propane? I've seen a lot of guys blame the liner material but sometimes it's the gas mix causing the corrosion. Did you notice if the pinhole was right at the bottom of the liner or up higher near the draft hood connection? I replaced a liner last year where the condensing flue gases were pooling at the bottom and eating through a brand new 316L in like 18 months. The heavy wall 304 makes a big difference but I'm wondering if your chimney had a drip leg issue. Just trying to figure out if it was a material problem or an installation problem.