Chimney Liner Alloy: 316Ti vs 304 Stainless — Which You Need
Stainless chimney liners are not all built for the same job. The difference between 304 and 316Ti comes down to which fuels each alloy survives, and picking the wrong one is a hidden failure that stays out of sight until the liner corrodes. This guide covers how to match the alloy to your fuel.
Of every decision made during a reline, the most consequential is invisible in the finished job: which stainless alloy went up the flue. Quotes will name two options, 304 and 316Ti, and they are not interchangeable, because each survives a different set of fuels and exhaust chemistries. Put the cheaper alloy where the harsher one belongs and you get a failure that hides until the liner corrodes from the inside. Weighed against the cost of relining twice, the small added cost of getting the alloy right once is trivial, which is exactly why it matters who specs the job.
01304 stainless — the wood-burning standard
304 stainless steel earns its place as a strong, corrosion-resistant alloy and the appropriate, code-recognized choice for many wood-burning appliances. Exhaust from a clean wood fire is comparatively benign, and a correctly sized, correctly installed 304 liner stands up to it over a long service life. On a straightforward wood-burning reline where the system will stay wood-burning, 304 is often exactly the right specification, and selling a harsher-duty alloy nobody needs is no more honest than under-speccing the one they do.
There is a limit to 304's resistance, and the acidic, condensing exhaust of certain other fuels crosses it. An alloy perfectly suited to a wood flue can pit and fail inside 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 designates a titanium-stabilized 316 stainless. Resistance to the chloride and acid attack found in tougher exhaust streams is what the molybdenum in 316 sharply improves, while the titanium stabilization protects the weld-affected zones from a specific corrosion failure under heat. What that delivers in practice 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.
Nowhere is the case for 316Ti clearer than in high-efficiency gas and oil appliances. Those units extract so much heat that 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. Whenever there is doubt, or a single liner has to stay future-proof against a later fuel conversion, 316Ti is the alloy that never has to be revisited.
03Why the wrong alloy is a hidden, expensive mistake
Corrosion attacks a liner from the inside, where you will never see it, so an under-specced alloy gives no warning at all. Failure arrives years early, often surfacing as a breach at the next camera inspection or, worse, as a venting problem that puts combustion gases where they should not be. Once the symptom appears, relining again is the only fix. The cheap quote that saved a few hundred dollars on alloy ends up being the most expensive liner you will ever buy.
Cheap installs cut a second corner in the same place: the non-connected slammer liner dropped into an oversized flue, venting into a void where it condenses and underperforms regardless of alloy. A reline done to the standard 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 one part you cannot inspect later, which makes it the part that most needs honest specification the first time.
Matching alloy to fuel is the whole rule: 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 stays the safe pick whenever the fuel might change. A wrong alloy remains invisible until it corrodes, so insist on a quote that names the alloy, sizes the liner to the appliance, and documents the install. Specified correctly once, 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.