Chimney Liner Alloy: 316Ti vs 304 Stainless — Which You Need
Not all stainless chimney liners are the same. What separates 304 from 316Ti stainless is which fuels they can survive, and picking the wrong alloy is a hidden failure you will not notice until the liner corrodes. Here is how to match the alloy to your fuel.
When a chimney gets relined, the single most consequential decision is the one you cannot see in the finished job: which stainless alloy went up the flue. The two you will find on a quote are 304 and 316Ti, and they are not interchangeable, since they survive different fuels and different exhaust chemistries, and putting the cheaper one where the tougher one belongs is a failure that stays hidden until the liner corrodes from the inside. The premium for getting the alloy right once is small next to 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 pick for many wood-burning appliances. The exhaust from a clean wood fire is comparatively mild, and 304 stands up to it well over a long service life when the liner is sized and installed correctly. For a straightforward wood-burning reline on a system that is staying wood-burning, 304 is often exactly the right specification, and paying for a harsher-duty alloy you do not need is no more honest than under-speccing one you do.
The catch is that 304's resistance has limits, and the acidic, condensing exhaust of certain other fuels crosses them. The alloy that is 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 guards the weld-affected zones against a specific corrosion failure under heat. What you get in practice is an alloy rated for all fuels, wood, gas, oil, and pellet, and the right call anywhere the exhaust is acidic or condensing, or anywhere the fuel might change down the road.
High-efficiency gas and oil appliances make the clearest case for 316Ti. They pull out so much heat that the flue gases cool and condense inside the liner, and that condensate is acidic enough to eat away at a lesser alloy. Coastal and high-chloride settings push the same way. When you are unsure, or when one liner has to be future-proof against a later fuel conversion, 316Ti is the alloy you never have to revisit.
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 gives no warning, it just fails years early, often turning up as a breach at the next camera inspection or, worse, as a venting problem that puts combustion gases where they do not belong. By the time the symptom shows, the only fix is to reline again. The cheap quote that saved a few hundred dollars on alloy becomes the most expensive liner you will 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 no matter what the alloy is. A proper reline is a full-length liner of the correct alloy, sized right to the appliance, insulated where code and performance call for it, with a continuous positive connection from the appliance collar to the cap, plus documentation proving all of it. The alloy is the part you cannot inspect later, so it is 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 stays 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.