316Ti or 304: Specifying a Liner Alloy Without Guessing
The alloy is the line on the quote that decides whether your liner lasts decades or needs replacing. It is chosen against your fuel, and it is frequently not stated at all.
A liner is a once-in-decades purchase and the single specification that determines its service life is the stainless alloy. It is also the line most often missing from a quote. Here is how the choice is actually made, so you can ask the question that matters.
01What the two alloys differ on
Both are stainless. The difference is resistance to acidic condensate — the corrosive product formed when flue gases cool below their dew point on the way up. 316Ti is titanium-stabilised and substantially more resistant to that attack. 304 is not, and does not need to be for every application.
So the choice is not 'better versus worse'. It is 'matched to the fuel versus not matched to the fuel', and the wrong match fails from the inside.
02Fuel is what decides it
Fuels that produce acidic condensate call for 316Ti. Applications that do not produce it can be served by 304 at lower cost, legitimately. The determining factor is what will be burned and what the appliance is, not the price tier a contractor is trying to hit.
If you may change appliance or fuel later, that belongs in the conversation now. Specifying for today's appliance and switching fuel in three years is a common route to an early replacement.
03Insulation is part of the specification, not an option
Insulation does two things. It allows the liner to carry its listing at reduced clearance to combustibles, and it keeps flue gases warmer on the way up — which reduces the condensation that drives the corrosion the alloy is resisting.
So the two decisions interact. An insulated liner is a milder chemical environment than an uninsulated one, and an uninsulated liner in a cold masonry chase is a slower, colder, dirtier flue that also loads deposit faster.
04The complete assembly is what carries the listing
A liner is compliant as a system: liner, insulation where required, top plate, cap, tee or connector, clamps. Substituting a generic connector into a listed system is not a small economy — the listing covers the components together.
Ask whether the quote is for the complete listed kit. A price that looks unusually low is frequently a price for the pipe.
05What to ask before signing
Which alloy, and why — expect the answer to reference your appliance and fuel rather than a package name. Whether insulation is included and to what thickness. Whether the quote covers the complete listed assembly. And to see the camera scan that established the liner was needed at all.
Four questions. They take a minute and they are the difference between buying this once and buying it twice.
Ask which alloy and why. If the answer does not reference your fuel and appliance, the specification has not been made — a price has. This is the one component in the trade where the cheap version reliably costs more.
Every recommendation in this guide starts from one place: a graded, photographed inspection. Book a inspection and pair it with a chimney liner installation — one standard, one paper trail, every job.