DuraVent DuraFlex Pro Basic Kit: a liner and fittings for chimneys with several bends
The DuraVent DuraFlex Pro Basic Kit is a liner kit with top fittings and a bottom connector. DuraFlex Stainless is DuraVent’s flexible stainless steel liner for relining a masonry chimney that vents a wood, pellet, oil, or gas appliance. Pro is DuraVent’s most flexible liner. Its 316 stainless steel has deeper ridges and uses 20 percent more steel in each foot, letting it bend around several turns. The liner arrives straight. The box also holds a chimney top plate with a welded storm collar that sheds rain, a removable cap, and the connector.
Choose a length of 15, 20, 25, 30, or 35 feet, then a diameter from 3 to 8 inches, including 5 1/2 inch. Pro shares fittings and insulation wraps with DuraFlex 304 and 316, which suit chimneys with fewer bends. For a fireplace insert, the liner passes through the old damper opening into the firebox. Ceramic blanket seals the space around it above the insert to keep room air from escaping up the chimney. Insulation is sold separately. Connecting through the chimney wall? See the DuraVent DuraFlex Pro Tee Kit. The DuraVent DuraFlex Pro Basic Kit ships free from My Cozy Outdoors with No Sales Tax (except WY) and the full manufacturer warranty.
Details
SKU: 3DFPRO-15K | 4DFPRO-15K | 5DFPRO-15K | 55DFPRO-15K | 6DFPRO-15K | 7DFPRO-15K | 8DFPRO-15K
SKU: 3DFPRO-20K | 4DFPRO-20K | 5DFPRO-20K | 55DFPRO-20K | 6DFPRO-20K | 7DFPRO-20K | 8DFPRO-20K
SKU: 3DFPRO-25K | 4DFPRO-25K | 5DFPRO-25K | 55DFPRO-25K | 6DFPRO-25K | 7DFPRO-25K | 8DFPRO-25K
SKU: 3DFPRO-30K | 4DFPRO-30K | 5DFPRO-30K | 55DFPRO-30K | 6DFPRO-30K | 7DFPRO-30K | 8DFPRO-30K
SKU: 3DFPRO-35K | 4DFPRO-35K | 5DFPRO-35K | 55DFPRO-35K | 6DFPRO-35K | 7DFPRO-35K | 8DFPRO-35K
Applications
- DuraFlex Pro ultra flexible relining for masonry chimney. Use with gas, wood pellet, oil, or wood appliances. Applications include: fireplace inserts, furnaces, boilers, and water heaters.
- DuraFlex SW smooth wall flexible relining for masonry chimney. Use with gas, wood pellet, oil, or wood appliances. Applications include: fireplace inserts, furnaces, boilers, and water heaters.
- DuraFlex 316 flexible relining for masonry chimney. Use with gas, wood pellet, oil, or wood appliance. Applications include: fireplace inserts, furnaces, boilers, and water heaters. 316 is designed for use in harsher conditions, for more resistance to corrosion, such as coal.
- DuraFlex 304 flexible relining for masonry chimney. Use with gas, wood pellet, oil, or wood appliances. Applications include: fireplace inserts, furnaces, boilers, and water heaters.
Materials and Construction
DuraFlex Pro: Single-wall .005″ 316 stainless steel.
DuraFlex SW: Single-wall .005″ overlapped 316 stainless steel (totalling .010″). Overlapped to create smooth inner wall.
DuraFlex 316 & 304: Single-wall .005” 316 or 304 stainless steel.
Clearances
DuraFlex Pro: 0″ clearance for gas, oil, and pellet applications. 1″ clearance to masonry for wood-burning applications. Insulation is required for 0″ clearance to masonry for wood-burning.
DuraFlex SW: Clearances 0″ clearance for gas, oil, and pellet applications. ” clearance to masonry for wood-burning applications. Insulation is required for 0” clearance to masonry for wood-burning.
DuraFlex 316 & 304: 0″ clearance for gas, oil, and pellet applications. 1″ clearance to masonry for wood-burning applications. Insulation is required for 0″ clearance to masonry for wood-burning.
Diameters
DuraFlex Pro & SW: 3″ – 12″.
DuraFlex 316 & 304: 3″ – 8″.
Listings
DuraFlex Pro: Listed to UL 1777 and ULC S635 (MH45609).
DuraFlex SW: Listed to UL 1777 (MH45609).
DuraFlex 316 & 304: Listed to UL 1777 and ULC S635 (MH45609).
FAQ
What is in the DuraFlex Pro Basic Kit, and how do I size it?
The kit has a DuraFlex SS Top Plate with welded Storm Collar, a Removable Vertical Cap, a DuraFlex SS Connector and one length of DuraFlex Pro liner. Choose the flex length (15, 20, 25, 30 or 35 feet) and then the diameter (3 to 8 inch) on the selectors above; the liner diameter should match the appliance outlet and the length must reach from the connection to the chimney top.
What is a chimney liner, and when do I need one?
A liner is a continuous stainless flue that runs inside a masonry chimney so the exhaust never touches damaged, unlined or oversized brick and tile. DuraFlex Pro is UL 1777 listed as an alternative to clay tiles for fireplace inserts, wood and pellet stoves, furnaces, boilers and water heaters burning gas, oil, pellets or wood, whether the old tiles stay in place or are removed.
Does the liner have to be insulated?
For gas, oil and pellet appliances no clearance or insulation is required, though DuraVent notes insulation improves draft and cuts condensation, especially on exterior chimneys. For wood burning the liner needs 1 inch of clearance to the masonry, or a 1/2-inch ProFoil or Flexwrap blanket (or 1 inch of TherMix) to be listed at zero clearance; the ProMesh Insulation Kit is sold separately.
Basic Kit or Tee Kit: which one do I need?
The Basic Kit’s connector suits an installation where the liner drops straight down to the appliance, such as a fireplace insert or a stove sitting in the fireplace opening. When the appliance connects through the chimney wall from the side, choose the Pro Tee Kit instead, which swaps the connector for a tee with a clean-out. Both use the same top plate and cap.
Can the liner be cut or squeezed to fit a tight flue?
Yes. Cut DuraFlex Pro to length with a hacksaw or a reciprocating saw with a metal blade, and a round liner that will not pass the flue can be ovalized; ovalizing reduces the cross-section, so follow DuraVent’s L1244 guidance. Pro is the most flexible DuraFlex, with 20 percent more stainless per foot, which is what lets it snake past offsets and smoke shelves.
How long will a stainless liner last, and what does the warranty need?
DuraFlex Pro is made of corrosion-resistant 316 stainless steel and is covered by DuraVent’s limited lifetime warranty to the original purchaser. The warranty conditions in the manual call for installation per the instructions, a chimney cap, annual inspection and cleaning by a qualified sweep, and no chemical chimney cleaners; chimney-fire damage is excluded.
Which fuels can I vent through DuraFlex Pro?
Gas, oil, wood pellets and wood are all listed, which is why one liner can serve a wood insert today and a gas insert later. Because it is 316 stainless it is also the grade DuraVent recommends where corrosion is harsher, such as coal. The 0-inch clearance for gas, oil and pellets and the insulated wood rule apply to every fuel you switch to.