A flexible stainless steel flue liner is normally used to line an existing residential brick chimney where there . The flex liner can be inserted at the top of the chimney by one operative and pulled down from below by the second operative.
Due to the flexibility of the liner it is generally able to negotiate offsets in the route more easily than if a rigid stainless steel liner was used for the same purpose. The most common size of liner used is 5" Flexible Liner for use with a DEFRA approved stove for smokeless zones, or 6" Flexible Liner for stoves without the DEFRA approvals.
You would think that one liner is as good as another, just as long as it was stainless and flexible, right? WRONG! All liners are not made the same and each different flexible liner solution has its own particular method of installation, as approved by the flex manufacturer. If it's not installed to the manufacturers recommendations, then quite simply they normally won't honor the guarantee that comes with the product.
Manufacturers Warranty/Guarantee for flexible liners vary massively in both timescale and requirements to initiate the warranty should something go wrong with the liner. We will talk about this in our installment 'Flexible Liner Guarantees & Warranties'.
Now here's the REAL difference in flexible liner manufacture...
The difference in the manufacturing is the difference in the flexible liner rigidity and convolution tightness. All stainless steel chimney liners can be grade 316 or Grade 904 stainless steel, but some liners are so much more rigid than others and that's why there's a distinct difference in the purchase price. If the price is too good to be true then generally the flexible liner will be of a light gauge flex, and invariably the convolutions will not be as tight in keeping it together as a more expensive liner. If a liner is too rigid and your chimney has an offset in it, a more rigid flex will make it extremely difficult to pull the liner down to your appliance spigot. If you can stand on the liner and it doesn't flatten then its very robust indeed, but perhaps not so good for chimneys with offsets in them.
If the liner is super flexible and lightweight it may be the case that it will simply unravel or just split apart as you pull it through the brick chimney before it even reaches the fireplace. We would highly recommend paying a mid-range price for your 316 flexible liner to ensure that it will meet with your requirements and be robust enough to last 10+ Years of cold days and nights.
We all know that keeping your purchase costs down are very important factors in making solid fuel system purchases; but the main thing to consider is the trade-off between quality and longevity. If you pay too cheaply for your chimney parts you're no doubt going going to end up paying a more expensive price for replacing those parts in the long term when they fail, AND THEY WILL!