how to install b vent through wall

Installing a B-vent (also known as a Type B vent) through a wall is a common method for venting gas appliances like a water heater or furnace. B-vent systems are designed for appliances that use natural draft for exhaust. Here’s a step-by-step guide on how to install a B-vent through a wall:

Materials You’ll Need:

  • B-vent pipe sections
  • B-vent elbow(s) (if needed)
  • Wall thimble (adjustable or fixed)
  • Storm collar
  • Roof flashing (if venting through the roof)
  • High-temperature silicone sealant
  • Screws or fasteners
  • Screwdriver or drill
  • Measuring tape
  • Level
  • Safety gear (gloves, safety glasses)


  1. Check Local Codes: Before you begin, check local building codes and regulations regarding the installation of B-vent systems. Make sure your installation complies with these codes.
  2. Determine the Vent Route: Decide on the route for the B-vent, taking into account the location of the gas appliance, the shortest and most direct route to the exterior, and any obstructions in the wall.
  3. Measure and Cut B-Vent: Measure the distance from the appliance to the exterior wall. Cut the B-vent pipe sections to the appropriate length using a hacksaw or reciprocating saw. If you need an elbow to navigate around obstructions, use a B-vent elbow.
  4. Install the Wall Thimble:
    • If you are venting horizontally through a wall, you’ll need to install a wall thimble. Mark the desired location on the wall, ensuring it aligns with the B-vent pipe’s position.
    • Cut a hole in the wall using a saw or drill to accommodate the thimble.
    • Insert the wall thimble through the hole, ensuring it fits securely.
    • If using an adjustable wall thimble, adjust it to the desired wall thickness and secure it in place using screws or fasteners. A fixed wall thimble is secured using screws as well.
  5. Install the B-Vent Pipe:
    • Connect the B-vent pipe sections and any elbows as needed to create a continuous vent pipe from the appliance to the wall thimble.
    • Slide one end of the B-vent pipe through the wall thimble and position it so that it slopes slightly upward toward the exterior. This slope helps with proper draft.
    • Ensure that the pipe is securely connected and properly supported using brackets or straps.
  6. Seal and Secure: Apply high-temperature silicone sealant around the joint between the B-vent pipe and the wall thimble. This helps create an airtight seal.
  7. Install Storm Collar:
    • Place a storm collar around the B-vent pipe on the exterior side of the wall. The storm collar prevents water from entering the wall thimble.
    • Secure the storm collar in place using screws or fasteners.
  8. Complete the Exterior Installation:
    • If the B-vent continues through the roof, install roof flashing around the vent pipe at the roof penetration point to prevent leaks.
    • Secure the vent pipe to the roof using appropriate supports or brackets.
  9. Final Inspection: Double-check all connections, joints, and seals to ensure they are secure and properly sealed. Make sure the vent pipe is stable and well-supported.
  10. Test the Appliance: Before using the gas appliance, test it to ensure it functions correctly and that the B-vent is properly venting exhaust gases to the outside.
  11. Regular Maintenance: Periodically inspect the B-vent system for any signs of wear, corrosion, or damage. Address any issues promptly to maintain safe and efficient venting.

Always follow the manufacturer’s instructions for your specific B-vent system and consult with a professional if you are unsure about any aspect of the installation. Proper installation and maintenance of the B-vent system are essential for the safe operation of gas appliances.

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