Chimney Liner Alloy: 316Ti vs 304 Stainless — Which You Need
Not all stainless chimney liners are equal. The difference between 304 and 316Ti stainless is which fuels they survive — and choosing the wrong alloy is a hidden failure you won't see until the liner corrodes. Here's how to match the alloy to your fuel.
When a chimney is relined, the single most consequential decision is invisible from the finished job: which stainless alloy went up the flue. The two you'll see on a quote are 304 and 316Ti, and they are not interchangeable — they survive different fuels and different exhaust chemistries, and installing the cheaper one where the harsher one belongs is a failure that hides until the liner corrodes from the inside. The premium of getting the alloy right once is small against the cost of relining twice, which is exactly why it matters who specs the job.
01304 stainless — the wood-burning standard
304 stainless steel is a strong, corrosion-resistant alloy and the appropriate, code-recognized choice for many wood-burning appliances. The exhaust from a clean wood fire is comparatively benign, and 304 holds up to it well over a long service life when the liner is correctly sized and installed. For a straightforward wood-burning reline on a system that will stay wood-burning, 304 is often exactly the right specification — and paying for a harsher-duty alloy you don't need is no more honest than under-speccing one you do.
The catch is that 304's resistance has limits, and those limits are crossed by the acidic, condensing exhaust of certain other fuels. The alloy that's perfect for a wood flue can pit and fail in a high-efficiency gas or oil flue, which is why the fuel — not the budget — has to drive the choice.
02316Ti — the all-fuel, harsher-duty alloy
316Ti is a titanium-stabilized 316 stainless. The molybdenum in 316 sharply improves resistance to the chloride and acid attack found in tougher exhaust streams, and the titanium stabilization protects the weld-affected zones from a specific corrosion failure under heat. The practical result is an alloy rated for all fuels — wood, gas, oil, and pellet — and the right call wherever the exhaust is acidic or condensing, or wherever the fuel might change in the future.
High-efficiency gas and oil appliances are the clearest case for 316Ti. They extract so much heat that the flue gases cool and condense inside the liner, and that condensate is acidic enough to attack a lesser alloy. Coastal and high-chloride environments push the same direction. When in doubt, or when a single liner has to be future-proof against a later fuel conversion, 316Ti is the alloy that doesn't have to be revisited.
03Why the wrong alloy is a hidden, expensive mistake
A liner corrodes from the inside, where you will never see it, so an under-specced alloy doesn't announce itself — it simply fails years early, often as a breach discovered at the next camera inspection or, worse, as a venting problem that puts combustion gases where they shouldn't be. By the time the symptom appears, the only fix is to reline again. The cheap quote that saved a few hundred dollars on alloy becomes the most expensive liner you'll ever buy.
This is also where cheap installs cut a second corner: a non-connected "slammer" liner dropped into an oversized flue, venting into a void where it condenses and underperforms regardless of alloy. A premium reline is a full-length liner of the correct alloy, sized correctly to the appliance, insulated where code and performance require it, with a continuous positive connection from the appliance collar to the cap — and documentation proving all of it. The alloy is the part you can't inspect later, so it's the part you most need specified honestly the first time.
Match the alloy to the fuel: 304 stainless is the right, cost-appropriate liner for many wood-burning systems, while 316Ti is the all-fuel, harsher-duty choice that survives the acidic, condensing exhaust of high-efficiency gas and oil — and the safe pick whenever the fuel might change. The wrong alloy is invisible until it corrodes, so insist on a quote that names the alloy, sizes the liner to the appliance, and documents the install. Get it right once and a stainless reline can last the remaining life of the home.
Every recommendation in this guide starts from one place: a graded, photographed inspection. Book a chimney inspection and pair it with a chimney liner — one standard, one paper trail, every job.