DuraFlex AL (DFAL) aluminum flexible relining for masonry chimney. Use with natural gas or liquid propane category I, draft hood equipped appliances, and appliances tested and listed to use Type B Gas Vent. Applications include: natural gas fireplaces, gas-fired furnaces, boilers, water heaters, and wall or space heating applications.
Materials and Construction
Single-wall .010" aluminum (2-ply of .005").
0" clearance to masonry.
3", 4", 5", 5 ½", 6", 7", and 8".
Listed to UL 1777 and ULC S635.
Refer to our Typical Venting Installation drawings to select the appropriate component parts for your installation.
More Typical Installations:
|Installation Key |
|1 ||DuraCap |
|2 ||Storm Collar |
|3 ||Roof Flashing |
|4 ||High-Wind Cap |
|5 ||Round Pipe |
|6 ||Elbow |
|7 ||Tee |
|8 ||Tee Cap |
|9 ||Increaser Tee |
|10 ||Female Flex Adapter |
|11 ||Male Adapter |
|12 ||Double-Wall Wye |
|13 ||Pipe Collar |
|14 ||Increaser |
|15 ||Draft Hood Connector |
|16 ||Square Firestop Support |
|17 ||Oval Pipe |
|18 ||Oval to Round Adapter |
|19 ||Oval Tee |
|20 ||Oval Tee Cap |
|21 ||Oval Tee Support |
|22 ||Oval Firestop Spacer |
|23 ||DuraConnect II |
|24 ||DuraFlex AL Length |
|25 ||DuraFlex Motar Sleeve |
|26 ||DuraFlex AL Coupling |
How Size and Height Affect Stove Performance
- The amount of heat the vent gases lose as they flow determines how much condensation will occur and how strong the draft will be. To control the heat loses, proper selection of venting materials is of vital importance.
- Double-wall Type B Gas Vent, with an aluminum inner wall and a galvanized steel outer wall, has proven to be the ideal choice in venting materials.
Vent Termination Chart
Using listed Type B Gas Vent caps may terminate in accordance with this table.
|Minimum height |
|Roof Pitch ||Feet ||Meters |
|Flat to 7/12 ||1 ||0.30 |
|Over 7/12 to 8/12 ||1.5 ||0.46 |
|Over 8/12 to 9/12 ||2 ||0.61 |
|Over 9/12 to 10/12 ||2.5 ||0.76 |
|Over 10/12 to 11/12 ||3.25 ||0.99 |
|Over 11/12 to 12/12 ||4 ||1.22 |
|Over 12/12 to 14/12 ||5 ||1.52 |
|Over 14/12 to 16/12 ||6 ||1.83 |
|Over 16/12 to 18/12 ||7 ||2.13 |
|Over 18/12 to 20/12 ||7.5 ||2.29 |
|Over 20/12 to 21/12 ||8 ||2.44 |
Gas Vent Specification Chart
|Item ||Clearances ||Maximum Height ||Outer Tube Ø ||Materials ||Locking Device ||UL Listing ||ULC Listing |
|Type B Vent Round 3"-8" ||1 inch to combustibles ||100 feet ||5/8" larger than ID ||Inner - .012" Aluminum Outer - .018" Galvanized ||DuraLock ||MH6357 ||CMH1276 |
|Round 10" to 16" See note 2 ||1 inch to combustibles ||100 feet ||1" larger than ID ||Inner - .016" Aluminum Outer - .021" Galvanized ||TwistLock Screws ||MH6357 ||CMH1276 |
|Round 18" to 30" ||1 inch to combustibles ||100 feet ||2" larger than ID See note 5 ||Inner - .020" Aluminum Outer - .021" Galvanized ||Screws ||MH6357 ||CMH1276 |
|Oval Type B Vent 4" and 5" ||2" x 4" & 2" x 6" stud wall and 1 inch to combustibles ||See Note 3 ||2 1/2" x 7 1/4" 3 1/8" x 10 7/8" ||Inner - .012" Aluminum Outer - .018" Galvanized ||Button Lock ||MH6357 ||CMH1276 |
|Oval Type B Vent 6" ||2" x 6" stud wall and 1 inch to combustibles ||See Note 3 ||3 1/4" x 12" ||Inner - .012" Aluminum Outer - .018" Galvanized ||Button Lock ||MH6357 ||CMH1276 |
|Type B Vent 3" to 6" Round Liner" ||0"/Masonry ||50 feet ||5/8" larger than ID ||Inner - .012" Aluminum Outer - .018" Galvanized ||DuraLock ||MH14420 MH6357 ||CMH1407 |
|DuraFlex AL Gas Relining 3" to 6" ||0"/Masonry ||50 feet ||1/4" larger than ID ||.010" Aluminum Flex ||Screws DuraLock ||MH14420 ||-- |
|DuraConnect 3" to 6" ||1 inch to combustibles ||See Note 4 ||1/4" larger than ID ||.010" Aluminum Flex .018" Galvalume ||DuraLock ||MH14089 ||-- |
|DuraConnect II 3" to 6" ||1 inch to combustibles ||See Note 4 ||1/4" larger than ID ||.010" Aluminum Flex .018" Galvalume ||DuraLock ||MH14089 ||-- |
- Clearance to combustibles is the air space between vent and combustibles.
- Maximum height varies with equipment over 50', for taller applications refer to SDV sizing handbook (L202). 14"-16" Pipe require screws.
- When oval is used on wall furnaces, minimum height required from bottom of furnace to cap is 12', minimum 16" stud space.
- Limited by sizing tables.
- 18" pipe OD is one inch larger than ID and 20" - 30" OD is 2" greater than ID.
M&G DuraVent Limited Lifetime Warranty
M&G DuraVent, Inc. (“DuraVent”) provides this limited lifetime warranty for all of its products with the exception of Ventinox® (lifetime), and PolyPro® (ten years). Subject to the limitations set forth below, DuraVent warrants that its products will be free from defects in material or manufacturing, if properly installed, maintained and used. DuraVent products are fully warranted if installed only by a professional installer. This Warranty is transferable from the original homeowner to the buyer of the home. This warranty does not cover normal wear and tear, smoke damage or damage caused by chimney fires, acts of God, or any product that was: (1) purchased other than from an authorized DuraVent dealer, retailer or distributor; (2) modified or altered; (3) improperly serviced, inspected or cleaned; or (4) subject to negligence or any use not in accordance with the installation instructions included with the product as determined by DuraVent. Installation instructions are available online at www.duravent.com under Support/Literature and through our Customer Service Department 800-835-4429 or email@example.com. This limited lifetime warranty applies only to parts manufactured by DuraVent.
DuraVent provides the following warranties for its products: One Hundred Percent (100%) MSRP 15 years from the date of purchase, and Fifty Percent (50%) thereafter, except for the following limitations on: all Termination Caps and DuraBlack® are warranted at One Hundred Percent (100%) for five years.
All warranty obligations of DuraVent shall be limited to repair or replacement of the defective product pursuant to the terms and conditions applicable to each product line. These remedies shall constitute DuraVent’s sole obligation and sole remedy under this warranty. This warranty provides no cash surrender value. The terms and conditions of this warranty may not be modified, altered or waived by any action, inaction or representation, whether oral or in writing, except upon the express, written authority of an executive officer of DuraVent.
Corn, bio-fuels, driftwood or other wood containing salt, preservative-treated lumber, plastic and household trash or garbage, or wood pellets containing such materials must not be burned in the appliance or fireplace. In case of a chimney fire, the chimney must be inspected and approved by a certified Chimney Sweep before reuse. After each annual inspection, maintenance, and cleaning, the certified Chimney Sweep must fill out and date the appropriate section of the warranty card provided with the chimney liner.
LIMITATIONS ON INTERNET SALES: Notwithstanding any other terms or conditions of this Limited Lifetime Warranty, DuraVent provides no warranty for the following specific products if such products are not installed by a qualified professional installer: DuraTech®, DuraPlus HTC®, DuraChimney® II, PelletVent Pro®, DirectVent Pro®, FasNSeal®, FasNSeal® W2, FasNSeal® Flex, and PolyPro®, and M&G DuraVent’s relining products including DuraLiner®, DuraFlex® (SW, Pro, 316, 304), and Ventinox®. For purposes of this warranty, a trained professional installer is defined as one of the following: licensed contractors with prior chimney installation experience, CSIA Certified Chimney Sweeps, NFI Certified Specialists, or WETT Certified Professionals.
DuraVent must be notified and given the opportunity to inspect defective product prior to replacement under the terms of this limited lifetime warranty. All warranty claims must be submitted with proof of purchase. Labor and installation costs are not covered under this warranty. To obtain warranty service contact: DuraVent Warranty Service, 877 Cotting Ct., Vacaville CA 95688, or call 800-835-4429.
WHERE LAWFUL, DURAVENT DISCLAIMS ALL OTHER WARRANTIES, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT WILL DURAVENT BE LIABLE FOR INCIDENTAL, CONSEQUENTIAL, PUNITIVE OR SPECIAL DAMAGES OR DIRECT OR INDIRECT LOSS OF ANY KIND, INCLUDING BUT NOT LIMITED TO PROPERTY DAMAGE AND PERSONAL INJURY. DURAVENT’S ENTIRE LIABILITY IS LIMITED TO THE PURCHASE PRICE OF THIS PRODUCT. SOME STATES DO NOT ALLOW LIMITATIONS ON IMPLIED WARRANTIES, OR THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THE ABOVE LIMITATIONS AND EXCLUSIONS MAY NOT APPLY TO YOU. THIS LIMITED WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, AND YOU MAY ALSO HAVE OTHER RIGHTS THAT VARY FROM STATE TO STATE.
M&G DuraVent Limited Lifetime Warranty (PDF, 146KB )