Metal-fab 3M12 Double Wall B-vent Pipe 3x12 in Twist Lock

Product Description

The METAL-FAB 3M12 is a double-wall, round Type B gas vent pipe section designed for venting natural gas and propane appliances in residential and light-commercial applications. The inner wall is 0.012-inch aluminum alloy and the outer wall is 0.018-inch G90 galvanized steel, with an integral annular insulating air space between the two walls. This construction maintains flue gas temperature and reduces condensation risk. The section measures 3 inches in diameter and 12 inches in length and connects using a positive twist-lock end design that requires no additional adapters or field measuring. Licensed gas technicians and HVAC service professionals install this pipe as part of a listed B-vent system.

The 3M12 is suited for residential gas furnaces, boilers, water heaters, and similar Category I appliances that require a Type B vent. The twist-lock male and female ends come factory assembled, making the section ready to install directly from the box. This eliminates the custom cutting and adapter work common with rigid straight-pipe sections, reducing labor time when connecting appliances to an existing rigid B-vent system. It functions as a universal connector between appliance collars and rigid B-vent pipe runs where a short, flexible-length section is needed.

Key Features

• Double-wall construction with 0.012-inch aluminum alloy inner wall and 0.018-inch G90 galvanized steel outer wall
• Integral annular insulating air space maintains flue gas temperature and limits heat transfer to surrounding structure
• Positive twist-lock ends are factory assembled — no field cutting, special adapters, or measuring required
• Rated to 530 degrees F for safe use in standard Category I venting applications
• Meets UL 441 and NFPA 54/211 standards for Type B gas vent systems
• Made in USA

Compatibility

Designed as an OEM-style replacement and standard section for residential and light-commercial Type B gas vent systems using 3-inch diameter B-vent pipe with twist-lock connections.

Installation Notes

Installation must be performed by a qualified gas technician or licensed HVAC professional in accordance with NFPA 54, NFPA 211, and applicable local codes. Shut off gas supply and allow the venting system to cool completely before servicing or replacing any vent section. Maintain required clearances to combustibles as specified by the vent system manufacturer and local code. Do not mix vent pipe brands or connection types within the same listed vent system without confirming cross-brand compatibility with the manufacturer.

Technical Specifications

• Pipe Diameter: 3 inches
• Length: 12 inches
• Wall Type: Double Wall, Round
• End Type: Twist Lock
• Inner Wall Material: Aluminum Alloy
• Outer Wall Material: G90 Galvanized Steel
• Inner Wall Thickness: 0.012 inches
• Outer Wall Thickness: 0.018 inches
• Temperature Rating: 530 degrees F
• Applicable Standards: UL 441, NFPA 54/211
• Country of Origin: USA

Standard Information

• Brand: METAL-FAB
• Manufacturer Part Number: 3M12